Samenvatting Human Biology - Wiki

1 HUMAN BIOLOGY, SCIENCE, AND SOCIETY
2 THE CHEMISTRY OF LIVING THINGS
2.1 ALL MATTER CONSISTS OF ELEMENTS
2.2 ATOMS COMBINE TO FORM MOLECULES
P. 32 Table 2.2!!
2.3 LIFE DEPENDS ON WATER
Properties of water important to living organisms:
• Water molecules are polar;
• Water is a liquid at body temperature;
• Water can absorb and hold heat energy.
Water is the biological solvent
- Solvent
= liquid in which other substances dissolve;
- Solute
= any dissolved substance;
- Hydrophilic molecules
= polar molecules that are attracted to water and interact with it easily;
- Hydrophobic molecules
= nonpolar, neutral molecules that do not interact with water and won’t dissolve in it.
Water helps regulate body temperature
- Water may prevent large increases in body temperature.
Recap
Most biological molecules dissolve readily in water because water is a polar molecule. The liquid
nature of water facilitates the transport of biological molecules. Water absorbs and holds heat and
can lower body temperature through evaporation.
2.4 THE IMPORTANCE OF HYDROGEN IONS
Acids donate hydrogen ions, bases accept them
- Water molecule hydrogen ion (H + ) and hydroxide ion (OH - )
- Acid
= any molecule that can donate an H + ion,
when added to pure water: higher H + concentration = acidic solution.
- Base
= any molecule that can accept an H + ion,
when added to pure water: lower H + concentration = basic or alkaline solution.
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The pH scale expresses hydrogen ion concentration
- pH scale
= measure of the hydrogen ion concentration of a solution,
ranges from 0 to 14
7 = neutral, which corresponds to a concentration of 10 -7 moles/liter
- pH of blood is 7,4
Buffers minimize changes in pH
- Buffer
= any substance that tends to minimize the changes in pH that might otherwise occur
when an acid or base is added to a solution, essential to homeostasis.
- Buffer pairs related molecules that have opposite effect: an acid and a base form,
they try to reach a chemical equilibrium.
- Bicarbonate and carbonic acid = most important buffer pair in the body.
Recap
Acids can donate hydrogen ions to a solution, whereas bases can accept hydrogen ions from a
solution. The pH scale indicates the hydrogen ion concentration of a solution. The normal pH of
blood is 7,4. Buffers help maintain a stable pH in body fluids.
2.5 THE ORGANIC MOLECULES OF LIVING ORGANISMS
Organic molecules
= molecules that contain carbon and other elements held together by covalent bonds.
Carbon is the common building block of organic molecules
- Complexity: Natural tendency to form four covalent bonds with other molecules
ideal structural component, it can branch in a multitude of directions.
- No limit to the size
macromolecules (consist of thousands/millions of smaller molecules)
Macromolecules are synthesized and broken down within the cell
- Dehydration synthesis
= process during which macromolecules are synthesized,
smaller molecules (subunits) are joined by covalent bonds.
requires energy
- Hydrolysis
= process during which macromolecules are broken down,
each time a covalent bond is broken, the equivalent of a water molecule is added.
releases energy
- Four classes of organic molecules: Carbohydrates; lipids; proteins; nucleic acids.
Recap
Carbon is a key element of organic molecules because of the multiple ways it can form strong
covalent bonds with other molecules. Synthesizing organic molecules requires energy, breaking them
down liberates energy. The four classes of organic molecules are carbohydrates, lipids, proteins and
nucleic acids.
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2.6 CARBOHYDRATES: USED FOR ENERGY AND STRUCTURAL SUPPORT
Carbohydrates:
backbone of carbon atoms with hydrogen and oxygen attached in a 2-to-1 proportion.
Monosaccharides are simple sugars
- Monosaccharides
simple structures consisting of carbon hydrogen and oxygen (1-2-1 ratio).
- Ribose, deoxyribose, glucose and fructose most important in humans.
Ribose and deoxyribose: five-carbon monosaccharides that are components of
nucleotide molecules.
Glucose: six-carbon monosaccharide, source of energy for the cell.
Oligosaccharides: More than one monosaccharide linked together
- Oligosaccharides
= short strings of monosaccharides linked together by dehydration synthesis.
- Sucrose
= disaccharide glucose + fructose
Lactose
= disaccharide glucose + galactose
- Glycoproteins
some oligosaccharides are bonded to cell-membrane proteins, that participate in linking
adjacent cells together and in cell-cell recognition and communication.
Polysaccharides store energy
- Polysaccharides
= thousands of monosaccharides joined together by dehydration synthesis,
cells store extra energy in the bonds of the polysaccharide molecule.
• Animals: glycogen, plants: starch.
- Glycogen
most important polysaccharide, long chain of glucose.
- Cellulose, different form of glucose polysaccharide,
plants structural support, humans can’t break it down: fiber.
Recap
Carbohydrates contain carbon, hydrogen and oxygen in a 1-2-1 ratio. Simple sugars such as glucose
provide immediate energy for cells. Complex carbohydrates called polysaccharides store energy and
provide structural support (only in plants).
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2.7 LIPIDS: INSOLUBLE IN WATER
Most important characteristic of the lipids: insoluble!
Triglycerides are energy-storage molecules
- Triglycerides
= synthesized from a molecule of glycerol and three fatty acids..
- Fatty acids
= chains of hydrocarbons that end in a carboxyl group (COOH)
• Saturated fats
have a full complement of two hydrogen atoms for each carbon in their tails. The
tails are fairly straight, allowing them to pack closely together.
solid at room temperature
• Unsaturated fats or oils
have fewer than two hydrogen atoms on one or more of the carbon atoms in the
tails. Double bonds form between adjacent carbons, putting kinks in the tails.
liquid at room temperature
- Triglycerides are stored in adipose tissue and are an important source of stored energy.
Phospholipids are the primary component of cell membranes
- Phospholipids
= modified form of lipid, the primary structural component of cell membranes.
bilayer:
polar heads orient toward the outer surface, nonpolar tails orient toward the interior.
Steroids are composed of four rings
- Steroids
= different than the previously described, insoluble in water,
consist of a backbone of three 6-membered carbon rings and one 5-membered carbon
ring, to which different groups may be attached.
- Cholesterol
= essential structural component of cell membranes, source of several important
hormones (including estrogen and testosterone).
Recap
Lipids are all relatively insoluble in water. Triglycerides are an important source of stored energy.
Phospholipids, an important component of cell membranes, have a polar head and two fatty acid
tails. Steroids, such as cholesterol, have a four-ring structure.
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2.8 PROTEINS: COMPLEX STRUCTURES CONSTRUCTED OF AMINO ACIDS
Amino acids
= single units which form a protein, have an amino group (NH 3 ) on one end, a carboxyl group (COOH)
on the other end, a C–H group in the middle and an additional group (R).
The body can synthesize 11 of the amino acids, but the other 9 have to be obtained from food.
Polypeptide
= a single string of 3 to 100 amino acids.
Protein
= a string of more than 100 amino acids which has a complex structure and function.
Protein function depends on structure
- Primary structure
= amino acid sequence;
- Secondary structure
= how the chain of amino acids is oriented in space
helixes and sheets;
- Tertiary structure
= how the protein twists and folds to form a three-dimensional shape,
depends in part on the amino acid sequence! (polar/nonpolar);
- Quaternary structure
= refers to how many polypeptide chains make up the protein and how they associate
with each other.
- Denaturation
= permanent disruption of protein structure leading to a loss of biological function,
by high temperature or changes in pH.
Enzymes facilitate biochemical reactions
- Enzyme
= protein that functions as a biological catalyst;
- Catalyst
= a substance that speeds up the rate of a chemical reaction without itself being altered
or consumed by the reaction.
• Reactants or substrates products
Recap
Proteins consist of strings of amino acids. The function of a protein relates to its shape, which is
determined by its amino acid sequence and the twisting and folding of its chain of amino acids.
Enzymes are proteins that facilitate biochemical reactions in the body. Without enzymes, many
biochemical reactions would occur too slowly to sustain life.
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2.9 NUCLEIC ACIDS STORE GENETIC INFORMATION
Nucleic acids
- DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)
DNA = genetic material in living things, directs everything the cell does;
RNA = responsible for carrying out the instructions of DNA:
• DNA contains the instructions for producing RNA;
• RNA contains the instructions for producing proteins;
• Proteins direct most of life’s processes.
- Nucleotides
= smaller molecular subunits that form DNA and RNA,
consist of a
• five-carbon sugar: deoxyribose,
• a single- or double-ringed structure containing nitrogen called a base,
(adenine, thymine, cytosine or guanine)
• one or more phosphate groups.
- Specific sequence of base pairs = the “code” for making a specific protein.
- DNA = two (mirrored) strands of nucleotides, held together by weak hydrogen bonds.
Recap
DNA and RNA are constructed of long strings of nucleotides. Double-stranded DNA represents the
genetic code for life and RNA, which is single-stranded, is responsible for carrying out those
instructions.
2.10 ATP CARRIES ENERGY
ATP carries energy
- ATP (adenosine triphosphate)
consists of an adenine, base five carbon sugar ribose and three phosphate groups.
breaking the bond between the last two phosphate groups releases energy:
ATP ADP + P i + energy
- ADP (adenosine diphosphate)
reaction is reversible, ATP can be made by reattaching P i to ADP.
Recap
ATP is a nearly universal source of quick energy for cells. The energy is stored in the chemical bonds
between phosphate groups.
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3 STRUCTURE AND FUNCTION OF CELLS
The cell doctrine:
- All living things are composed of cells and cell products
- A single cell is the smallest unit that exhibits all the characteristics of life
- All cells come only from preexisting cells
Cells products: materials composed of death cells and substances resulting from cellular activity.
Cells are the smallest living units and all cells derived from earlier cells, going all the way back to our
first cell, the fertilized egg.
3.1 CELLS ARE CLASSIFIED ACCORDING TO THEIR INTERNAL ORGANIZATION
Eukaryotes have a nucleus, cytoplasm and organelles
Basic structural components:
- A plasma membrane
forms the outer covering of the cell.
- A nucleus
= a membrane bound compartment that houses cell’s genetic material and functions as
its information center.
- Cytoplasm
= everything inside the cell except the nucleus,
it is composed of cytosol which carries a variety of microscopic structures called
organelles that carry out specialized functions.
Prokaryotes lack a nucleus and organelles
- A plasma membrane that is surrounded by a rigid wall.
- Their material is concentrated in a particular region, bur is not specifically enclosed
within a membrane bound nucleus.
- Lack most of organelles found in eukaryotes.
3.2 CELL STRUCTURE REFLECTS CELL FUNCTION
Eukaryotes are remarkably alike in their structural features regardless of which organism they come
from:
- All cells carry out certain activities to maintain life;
- There is a strong link between structure and function.
All cells must gather raw materials, excrete wastes, makes macromolecules and grow and reproduce:
- Most of the structural differences between cells reflect differences in function:
• Muscle cells contain numerous of mitochondria that produce the energy for muscle
contraction; many nerve cells are long and thin, the cells that line the kidney tubules are
cube shaped and tightly bound together, reflecting their role in the transport of water
and other molecules.
- In all organism cells are not very different in size, some organism have more cells than others.
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Cells remain small to stay efficient
One feature all cells have in common:
they are all small in one or more dimensions, requiring considerable magnification to be seen.
- The total metabolic activities of a cell are proportional to its volume of cytoplasma,
which is in effect it size. To support its activities, every cell needs raw materials in
proportion to its size. Every cell also need a way to get rid of its wastes
- All raw materials, energy and waste can enter or leave the cell only by crossing the
plasma membrane
- As objects get larger, their volume increases more than their surface area.
The larger a cell gets, the more likely that its growth and metabolism will be limited by its ability to
supply across the plasma membrane.
Microvilli
= microscopic projections of the plasma membrane
common in cells that transport substances into and out of the body.
Recap
Common features of nearly all eukaryotic cells are a plasma membrane, a nucleus, organelles and the
cytoplasm. Cells exchange materials with their environment across their plasma membrane. Cells are
small, because this makes them more efficient at obtaining nutrients and expelling wastes.
3.3 A PLASMA MEMBRANE SURROUNDS THE CELL
Plasma membrane
= exterior structure of a living cell.
- Permits the movement of some substances into and out cell and restricted the movement of
others.
- Allows the transfer of information across the membrane.
The plasma membrane is a lipid bilayer
Constructed of two layers of phospholipids (= lipid bilayer)+ cholesterol and various proteins.
- Phospholipids
have polar head and neutral nonpolar tails.
The two layers are arranged so that the nonpolar tails meet in the center of the
membrane. One layer of polar heads faces the watery solution on the outside of the cell,
and the other layer of polar heads faces the watery solution of the cell’s cytoplasm.
- Cholesterol
increases the mechanical strength of the membrane by preventing it from becoming
either too rigid or too flexible and prevents the phospholipids from moving around too
much and anchor the proteins within the membrane
- Proteins
provide the means for transporting molecules and information across the plasma
membrane. Plasma membrane proteins generally have one region that is electrically
neutral and another that is electrically charged (+ or -).
The charged regions tend to extend out of the membrane and thus are in contact with
water, the neutral portions are often embedded within the phospholipid bilayer.
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The phospholipid bilayer is very thin, many substances are restricted from passing through the
membrane unless there is some sort of channel or transport mechanism available.
- The plasma membrane of animal cells is not rigid.
Most cells contain a certain shape but it is mainly due to a supported network of fibers inside the
cell, the fluid within the cell and the limitations imposed by contact with surrounding cells, not
the stiffness of the plasma membrane itself.
- The phospholipids and proteins are not anchored to specific positions in the plasma membrane.
the plasma membrane of animal cells are often called fluid mosaic.
Recap
The plasma membrane is comprised of phospholipids, cholesterol and proteins. The proteins transfer
information and transport molecules across the membrane and provide structural support.
3.4 MOLECULES CROSS THE PLASMA MEMBRANE IN SEVERAL WAYS
The plasma membrane creates a barrier between the cells external environment and processes of life
going on within. Molecules pass the membrane in three major ways.
Passive transport: Principles of diffusion and osmosis
Passive transport
= transporting without requiring any energy.
- Diffusion
= the movement of molecules from one region to another as the result of these random
motion. The molecules will move from the area of high concentration and toward the
region of low concentration.
The net diffusion of molecules requires that there is a difference in concentration
between two points = concentration gradient.
Once the concentration of molecules is the same throughout the solution, a state of
equilibrium exist,
= molecules diffuse randomly but equally in all directions.
- Osmosis
= the plasma membrane is semipermeable:
it allows some substances to cross by diffusion but not others.
It is highly permeable to water but not to all ions or molecules.
= the net diffusion of water across a selectively permeable membrane.
Osmotic pressure
= the fluid pressure required to exactly oppose osmosis.
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Passive transport moves with the concentration gradient
Most substances cross cell membranes by passive transport and always respect to the
concentration gradient.
- Diffusion through the lipid bilayer
The lipid bilayer structure of the plasma membrane allows the free passage of some
substances while restricting other.
• Small uncharged nonpolar molecules can diffuse right through the lipid bilayer
dissolve in the lipid bilayer!
2 lipid soluble molecules:
‣ Oxygen
diffuses into the cells and is used up in the process of metabolism;
‣ Carbon oxide
= waste product of metabolism;
‣ Urea
= neutral waste product removed from the body by the kidneys.
- Diffusion through channels
Channels are constructed of proteins.
The size and shapes of these protein channels, as well as the electrical charges on the
various amino acid groups that the line the channel and determine which molecules can
pass through.
• Some channels are open all time.
The diffusion of any molecule through the membrane is determined by the
number of channels.
• Some channels are gated, they can open and close under certain conditions.
Gated channels are particularly important in regulating the transport ions in cells
that are electrically excitable which represent a number of the proteins
instrumental in transport .
- Facilitated transport
The molecule does not pass through a channel at all but attaches to a membrane
protein, triggering a change in the protein’s shape or orientation that transfers the
molecule to the other side of the membrane and release it there.
Once the molecule is released, the protein returns to its original form.
A transport molecule
= a protein that carries a molecule across the membrane.
Facilitated transport is highly selective for substances.
The direction of movement is always from a higher concentration to one of lower
concentration does not require energy!
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Active transport requires energy
Active transport
moves substances through the plasma membrane against their concentration gradient.
It allows a cell to accumulate essential molecules even when their concentration outside the cell
is relatively low and to get rid of molecules that it does not need.
The transport is accomplished by proteins and must have some source of energy.
Some proteins use the high energy molecule ATP.
They break down ATP into ADP and a phosphate group (P) and used the released energy to
transport one or more molecules.
They are sometimes called pumps.
Some pumps can transport several different molecules at once, even in both directions.
E.g. sodium-potassium pump.
Endocytosis and exocytosis move materials in bulk
Endocytosis
= process which moves materials into the cell.
Exocytosis
= process which moves materials out of the cell.
P. 60 fig. 3.10!!
Information can be transferred across the plasma membrane
Receptor proteins
span the plasma membrane and can receive and transmit information across the membrane.
This causes something to happen within the cell even though no molecules cross the membrane.
P. 60 fig. 3.11!!
The sodium-potassium pump helps maintain cell volume
The most critical task for a cell is maintaining its volume.
The plasma membrane is soft and flexible, it cannot withstand much stretching or high fluid
pressures.
Cells accumulate certain materials depending on what is available in their extracellular
environment: they contain a nucleus and organelles but even produce molecules
(amino acids, sugars, lipids, ions… necessary for the cell to function).
Water can diffuse across the plasma membrane which increase cell volume causing the cell to
swell and even rupture.
The way to avoid this is to keep the solute concentration in its cytoplasm identical to the
solute concentration of the extracellular fluid:
the cell gets rid of ions it doesn’t need in large quantities in exchange for those it must stockpile.
Fig. 3.12a
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Isotonic extracellular fluid also maintains cell volume
Tonicity
= relative concentration of solutes in two fluids.
Water can diffuse across the cell membrane, controlling cells volume depends on the tonicity of
the extracellular fluid.
- Isotonic
= extracellular solute concentration is the same as intracellular fluid,
cells maintain a normal volume.
- Hypertonic
= the extracellular concentration of solutes is higher than the intracellular fluid:
water diffuses out of the cells and the cells shrink.
- Hypotonic
= the extracellular concentration of solutes is lower than the intracellular fluid:
water enters and starts to swell.
Pure water is most hypotonic solution possible!
Recap
Molecules may move across the plasma membrane by diffusion, by passive or active transport or by
endocytosis/exocytosis. Sodium-potassium exchange pumps in the cell membrane are essential for
the regulation of cell volume. In addition, homeostatic regulatory processes keep the tonicity of the
extracellular fluid relatively constant.
3.5 INTERNAL STRUCTURES CARRY OUT SPECIFIC FUNCTIONS
The nucleus controls the cell
Nucleus
= information center of the cell, contains the genetic information in the form of long molecules
of DNA. DNA controls nearly all activities of the cell.
Nuclear membrane
= the outer surface of the nucleus consists of a double-layered membrane that keeps the DNA
within the nucleus.
Nuclear pores
= the nuclear membrane is bridged with this.
It is too small for DNA to pass but it permit the passage of certain small proteins and RNA
molecules.
Nucleolus
= components of ribosomes are synthesized.
They pass through the nuclear pores to be assembled into ribosomes in the cytoplasm.
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Ribosomes are responsible for protein synthesis
Ribosomes
= small structures composed of RNA and certain proteins that are floating freely in the cytosol or
are attached to the endoplasmic reticulum,
responsible for making specific proteins.
They assemble amino acids into proteins by connecting the appropriate amino acids in the
correct sequence according to an RNA template.
- Ribosomes attached to the ER
release their proteins into the folds of the ER.
Many of them are packaged in membrane-bound vesicles, transported to the cell
membrane and secreted.
- Free-floating ribosomes
generally produce proteins for immediate use by the cell.
The endoplasmic reticulum is the manufacturing center
Endoplasmic reticulum
= synthesizes most of the chemical compounds made by the cell.
The materials manufactured by the ER are often not in their final form. They are refined and
packaged by the Golgi Apparatus.
- Rough ER: the synthesis of proteins.
They are mostly synthesized by the attached ribosomes and released into the fluid filled
space of the ER. Sometimes they enter the smooth ER.
- Smooth ER: proteins are packed for transfer in the Golgi apparatus.
It also synthesize macromolecules other than proteins. Most are lipids, like hormones.
The Golgi apparatus refines, packages and ships
The Golgi apparatus
= the cell refining, packaging (in vesicles) and shipping center.
It contains enzymes that further refine the products of the ER into final form.
The contents of the Golgi apparatus move outward by slow but continuous process.
Vesicles: Membrane-bound storage and shipping containers
Vesicles
= membrane bound spheres that enclose something within the cell.
- Vesicles that ship and store cellular products
Enclose and transport the products of the ER and Golgi apparatus.
Each vesicle contains only one product of the many substances made by the Golgi
apparatus.
The contents of each vesicle depend on certain proteins in the vesicle membrane:
they determine which product is put into the vesicle and where the vesicle is sent.
- Secretory vesicles
Contain products destined for export from the cell.
They migrate to the plasma membrane and release their content outside the cell by
exocytosis.
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- Endocytotic vesicles
Enclose bacteria and raw materials from the extracellular environment.
They bring them into the cell by endocytosis.
- Peroxisomes and lysosomes
Contain enzymes so powerful that they must be kept within the vesicle to avoid
damaging the rest of the cell.
• Peroxisomes:
destroy various toxic wastes produced by the cell and destroy compound that
have entered the cell from outside.
• Lysosomes:
contain powerful digestive enzymes.
They fuse with endocytotic vesicles within the cell, digesting bacteria and other
large objects.
They also dissolve and remove damaged mitochondria and other cellular debris.
residual bodies: digestive task is complete. Can be stored in the cell but are
mostly eliminated by exocytosis.
Mitochondria provide energy
Mitochondria
= responsible for providing the cell most of its energy.
The number of mitochondria within cells differ according to the energy requirements of the cells.
Fig. 3.19!
Fat and glycogen: Sources of energy
Some cells store energy in raw form, these energy stores are not enclosed in any membranebound
container. Some store it as lipids, but it can also be stored as glycogen granules.
Muscle cells rely on glycogen granules rather than on fat deposits because the energy stored in
the chemical bonds of glycogen can be used to produce ATP more quickly than the energy
derived from fat.
Recap
The nucleus contains most of the cell’s genetic material. Ribosomes are responsible for protein
assembly. The endoplasmic reticulum manufactures most other cellular products in rough form. The
Golgi apparatus refines cellular products and packages them into membrane-bound vesicles. Some
vesicles store, ship and secrete cellular products, others digest and remove toxic waste and cellular
debris. Mitochondria manufacture ATP for the cell.
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3.6 CELLS HAVE STRUCTURES FOR SUPPORT AND MOVEMENT
The cytoskeleton supports the cell
Cytoskeleton
consists of a loosely structured network of fibers (microtubules and microfilaments).
Microtubules: tiny, hallow tubes composed of proteins,
Microfilaments: thin, solid fibers composed of proteins.
- They attach to each other and to proteins in the plasma membrane (glycoproteins) which
typically have carbohydrates group components.
- The cytoplasm forms a framework for the soft plasma membrane and supports and
anchors the other structures within the cell.
Cilia and flagella are specialized for movement
Cilia and flagella extend from the surface.
Cilia
= numerous, move materials along the surface of a cell with a brushing motion. They are
common on the surfaces of cells that line the airways and in certain ducts, within the body.
Flagella
= only found in sperm cells.
The whiplike movement of the flagellum moves the entire sperm from one place to another.
They are similar in structure and are composed primarily of protein microtubules held tighter by
connecting elements and surrounded by a plasma membrane.
Nine pairs of fused microtubules surrounds two single microtubules in the center. The entire
structure bends when temporary linkages form between adjacent pairs of microtubules, causing
the pairs to slide past each other. The formation and release of these temporary bonds requires
energy in the form van ATP.
Centrioles are involved in cell division
Centrioles
= short, rodlike microtubular structures located near the nucleus,
essential in the process of cell division because they participate in aligning and dividing the
genetic material of the cell.
Recap
The cytoskeleton forms a supportive framework for the cell. Cilia and flagella are specialized for
movement, centrioles are essential to cell division.
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3.7 CELLS USE AND TRANSFORM MATTER AND ENERGY
Metabolism
Metabolism
= sum of all of the chemical reactions in the organism.
In a single cell, thousands of different chemical reactions are possible at any one time.
Some are organized in metabolic pathways:
one reaction follows after anther in orderly and predictable patterns.
- Linear: the product from one chemical reactions becomes substrate for the next;
- Circular: substrate molecules enter and product molecules exit, but the basic chemical
cycle repeats over and over again.
1. Anabolism: molecules are assembled into larger molecules that contain more energy
(requires energy).
E.g. the assembly of many amino acids.
2. Catabolism: larger molecules are broken down (releases energy).
E.g. breakdown of glucose into water.
Nearly every chemical reaction requires a specific enzyme. The cell regulates and controls the rate of
chemical reactions through the specificity and availability of key enzymes.
The metabolic activities in a living cell require a lot of energy.
It is required for building the complex macromolecules found only in living cells and is also used to
power cellular activities (active transport and muscle contraction)
energy formed by catabolism of molecules that serve as chemical stores of energy.
(ATP = reaction is reversible)
Glucose provides the cell with energy
Glucose
= most readily available fuel, derived from food or stored glycogen.
If glucose is not available, cells may return to stored fats and even proteins for fuel.
Glucose is a six carbon sugar molecule:
- Glycolysis
= a six carbon glucose molecule is split into two 3 carbon pyruvate molecules.
energy is required to get the process started.
- The preparatory step
= pyruvate enters a mitochondrion.
A series of chemical reactions yields a two carbon molecule called acetyl CoA plus energy
- The citric acid cycle
= an acetyl CoA molecule is broken down completely by mitochondrial enzymes
and its energy is released.
Most of the energy is captured by certain high energy electron transport molecules.
- The electron transport system
= most of the energy derived from the original glucose molecule is used to phosphorylate
ADP, producing high energy ATP.
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Fats and proteins are additional energy sources
Normally blood glucose concentration remains fairly constant even between meals because
glycogen is constantly being catabolized to replenish the glucose that is used by cells.
Most of the body’s energy reserves do not take the form of glycogen.
The body stores only 1% of its total energy reserves as glycogen; 78% stored as fat and 21% as
protein. After glycogen, our bodies may utilize fats and proteins as an energy source.
Anaerobic pathways make energy available without oxygen
Cellular respiration requires oxygen to complete the chemical reactions of the citric acid cycle
and the electron transport chain. A small amount of ATP can be made by humans by anaerobic
metabolism for at least a brief period of time.
Glycolysis is an anaerobic metabolic pathway. In the absence of oxygen, glucose is broken down
by pyruvate but then the pyruvate cannot proceed through the citric acid cycle and electron
transport chain. Instead it is converted to lactic acid.(P. 77 fig. 3.31)
The amounts of ATP are very limited: only two molecules of ATP are produced per molecule of
glucose instead of the usual 36.
Recap
Metabolism refers to all of the cell’s chemical processes. Metabolic pathways either create molecules
and use energy (anabolism) or break them down an liberate energy (catabolism). The primary source
of energy for a cell is ATP, produced within mitochondria by the complete breakdown of glucose to
CO 2 and water. The process requires oxygen. Fats and proteins can also be used to produce energy.
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4 FROM CELLS TO ORGAN SYSTEMS
4.1 TISSUES ARE GROUPS OF CELLS WITH A COMMON FUNCTION
Tissue = group of specialized cells that are similar in structure and that perform common functions.
4.2 EPITHELIAL TISSUES COVER BODY SURFACES AND CAVITIES
Epithelial tissue
consist of sheets of cells that line or cover various surfaces and body cavities.
Glandular epithelia form the body’s glands.
Glands are epithelial tissues that are specialized to synthesize and secrete a product. (Exo/Endocrine)
Epithelial tissues are classified according to cell shape
- Squamous epithelium
= one or more layers of flattened cells,
Forms skin, blood vessels, lungs, mouth and throat and vagina.
- Cuboidal epithelium
= cube-shaped cells,
Forms kidney tubules, covers surface of the ovaries.
- Columnar epithelium
= tall, rectangular cells,
Lines parts of the digestive tract, certain reproductive organs and the larynx.
goblet cells secrete mucus
- Single epithelium = single layer of cells,
Stratified epithelium = multiple layers.
The basement membrane provides structural support
- Basement membrane
= supporting noncellular layer beneath the epithelial tissue, anchors the cells to the
connective tissue underneath,
composed primarily of protein secreted by the epithelial cells (cellular product).
- Cell junctions hold the cells together:
• Tight junctions
seal the plasma membranes tightly together (nothing can pass through),
important in epithelial layers that control the movement of substances in and
out of the body (e.g. digestive tract, bladder, tubules of the kidneys).
• Adhesion junctions
are looser in structure, allow some movement between cells so the tissues can
stretch and bend (e.g. skin).
• Gap junctions
connecting channels made of proteins that permit the movement of ions or
water between two adjacent cells (e.g. liver, hearth, some muscle tissue).
Recap
Epithelial tissue line body surfaces and cavities and form glands. They are classified according to
shape (squamous, cuboidal or columnar) and the number of layers (simple or stratified).
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4.3 CONNECTIVE TISSUE SUPPORTS AND CONNECTS BODY PARTS
Connective tissue supports the softer organs of the body against gravity and connects the parts of
the body together. It also stores fat and produces the cells of blood.
Most connective tissue have few living cells, their structure consist of nonliving, extracellular
material, the matrix, that is synthesized by connective tissue cells and released into the space
between them.
Fibrous connective tissues provide strength and elasticity
- Fibrous connective tissues connect body parts, providing strength, support and flexibility.
• Collagen fibers
made of protein, confer strength and are slightly flexible;
• Elastic fibers
made of the protein elastin, which can stretch without breaking;
• Reticular fibers
thinner fibers of collagen, that interconnect with each other.
- Various fibers are embedded in a ground substance consisting of water polysaccharides
and proteins. The ground substance contains several types of cells,
most importantly fibroblasts, cells responsible for producing and secreting the proteins
that compose the fibers.
- Classification:
• Loose connective tissue (areolar)
collagen and elastic fibers great flexibility, modest strength;
(internal organs, muscles, blood vessels)
• Dense connective tissue
more collagen, primarily oriented in one direction
strongest connective tissue, when pulled in the same direction,
can tear when pulled from the side;
(tendons, ligaments, lower layers of skin)
• Elastic connective tissue
high proportion of elastic fibers stretch easily (organs that change shape);
(stomach, bladder, vocal cords)
• Reticular connective tissue (lymphoid)
thin, branched reticular fibers that form an interconnected network,
serves as the internal framework of soft organs (liver, lymphatic system).
19

Specialized connective tissues serve special functions
- Cartilage
= transition tissue from which bone develops, maintains the shape of certain body parts
and protects and cushions joints,
consists primarily of collagen fibers.
Chondroblasts = cells that produce the ground substance of cartilage,
lacunae = small chambers in which cells become enclosed,
chondrocyts = mature cells.
does not contain blood vessels.
- Bone
contains only a few living cells, most of the matric consists of hard mineral deposits of
calcium and phosphate.
does contain blood vessels.
- Blood
consists of cells suspended in a fluid matrix called plasma. It is considered a connective
tissue because all blood cells derive from stem cells located within bone.
- Adipose tissue
= highly specialized for fat storage, has few connective tissue fibers and almost no
ground substance. Adipocytes (fat cells) occupy most of its volume.
Recap
Fibrous connective tissues provide strength and elasticity and hold body parts together. Among the
specialized connective tissues, cartilage and bone provide support, blood transports materials
throughout the body and adipose tissue stores energy in the form of fat.
4.4 MUSCLE TISSUES CONTRACT TO PRODUCE MOVEMENT
Muscle tissue consists of cells that are specialized to shorten, or contract, resulting in movement. It
is composed of tightly packed muscle fibers.
Skeletal muscles move body parts
Skeletal muscle tissue connects to tendons, which attach to bones, multiple nuclei.
Contraction movement of body parts.
= voluntary
Cardiac muscle cells activate each other
Cardiac muscle tissue is found only in the heart, only one nucleus.
There are gap junction between the ends of adjoining cells. They represent direct
electrical connections.
= involuntary
Smooth muscle surrounds hollow structures
- Smooth muscle surrounds hollow organs and tubes (blood vessels, digestive tract,
uterus, bladder), only one nucleus.
There are gap junctions between cells, so when one cell contracts, nearby cells contract.
= involuntary
Recap
The common feature of all muscle tissues is that they contract, producing movement.
20

4.5 NERVOUS TISSUE TRANSMITS IMPULSES
Nervous tissue
consists primarily of cells, specialized for generating and transmitting electrical impulses
throughout the body.
- Neurons
= cells that generate and transmit electrical impulses,
have three basic parts:
• The cell body;
• Dendrites;
• Axon.
- Glial cells
= supporting cells, do not transmit electrical impulses,
but protect neurons and supply them with nutrients
Recap
Nervous tissues serve as a communication network by generating and transmitting electrical
impulses.
4.6 ORGANS AND ORGAN SYSTEMS PERFORM COMPLEX FUNCTIONS
Organs
= structures composed of two or more tissue types joined together that perform a specific function.
The human body is organized by organ systems
Organ systems = groups of organs that together serve a broad function that is important to
survival either of the individual organism or of the species.
Tissue membranes line body cavities
- Tissue membranes
consist of a layer of epithelial tissue and a layer of connective tissue,
line each body cavity and form our skin:
• Serous membranes line and lubricate body cavities to reduce friction;
• Mucous membranes line the airways, digestive tract and reproductive passages,
goblet cells secrete mucus, which lubricates the membrane’s surface and entraps
foreign particles.
• Synovial membranes line the very thin cavities between bones in movable joints,
secrete a fluid that lubricates the joint.
• Cutaneous membrane is the skin.
Describing body position or direction
- Three planes (midsagittal, frontal, transverse) divide the body.
- Anterior posterior; proximal distal; superior inferior.
Recap
An organ consists of several tissue types that join together to perform a specific function. An organ
system is a group of organs that share a broad function important for survival. The body’s hollow
cavities are lined by tissue membranes that support, protect and lubricate cavity surfaces.
21

4.7 THE SKIN AS AN ORGAN SYSTEM
= integumentary system.
Skin has many functions
- Protection from dehydration;
- Protection from injury;
- Defense against invasion by bacteria and viruses;
- Regulation of body temperature;
- Synthesis of an inactive form of vitamin D;
- Sensation (touch, vibration, pain, temperature).
Skin consists of epidermis and dermis
Epidermis = outer layer, dermis = inner layer, resting on a supportive layer = hypodermis.
- Epidermal cells are replaced constantly
Epidermis consists of multiple layers of squamous epithelial cells, cells near the base
divide repeatedly pushing older cells toward the surface.
• Keratinocytes
produce a though and waterproof protein: keratin.
• Melanocytes
produce a dark-brown pigment: melanin.
accumulates inside keratinocytes and protects against ultraviolet radiation.
- Fibers in dermis provide strength and elasticity
Dermis is primarily dense connective tissue, consisting of collagen, elastic and reticular
fibers embedded in a ground substance of water, polysaccharides and proteins.
Fibers allow the skin to stretch and give it strength.
Papillae = small projections that contain sensory nerve endings and small blood vessels.
• Hair:
shaft above the surface and root beneath. Root is protected by the follicle.
• Smooth muscle:
attached to the base of the hair follicle.
• Sebaceous glands:
secrete an oily fluid that moistens and softens hair and skin.
• Sweat glands:
produce sweat (in which dermicidin = antibiotic peptide, is found),
regulates body temperature and protects against bacteria.
• Blood vessels:
supply the cells of the dermis with nutrients and remove their wastes, also help
regulate body temperature.
• Sensory nerve endings:
provide information about the outside environment.
- The skin synthesizes an inactive from of vitamin D (not known it which type of cell).
Recap
The skin is an organ because it consists of different tissues serving common functions. Functions of
skin include protection, temperature regulation, vitamin D synthesis and sensory reception.
22

4.8 MULTICELLULAR ORGANISMS MUST MAINTAIN HOMEOSTASIS
Internal environment of the organism = a clear fluid = interstitial fluid.
Homeostasis
= constancy of the conditions within the internal environment.
Homeostasis is maintained by negative feedback
Negative feedback control systems have the following components:
- A controlled variable
= any physical or chemical property that might vary from time to time and that must be
controlled to maintain homeostasis;
- A sensor or receptor
monitors the current value of the controlled variable and sends the information to the
control center;
- A control center
receives input from the sensor and compares it to the ‘set point’;
- An effector
takes the action to correct imbalance.
Negative feedback helps maintain core body temperature
(example of how negative feedback works)
Positive feedback amplifies events
A change in the controlled variable sets in motion a series of events that amplify the original
change, rather than returning it to normal.
Recap
All multicellular organisms must maintain homeostasis of their internal environment. In a negative
feedback control system, any change in a controlled variable sets in motion a series of events that
revers the change, maintaining homeostasis.
23

5 THE SKELETAL SYSTEM
5.1 THE SKELETAL SYSTEM CONSISTS OF CONNECTIVE TISSUE
Bones are the hard elements of the skeleton
- consists of nonliving extracellular crystals of calcium minerals
and living tissue (several types of cells, nerves, blood vessels).
- Five important functions: support, protection, movement, blood cell formation and
mineral storage.
Bone contains living cells
- Long bones: diaphysis with an epiphysis at each end.
- Dense compact bone forms the shaft and covers each end.
The central cavity in the shaft is filled with yellow bone marrow(fat for energy),
the outer surface is covered by the periosteum (though layer of connective tissue),
which contains specialized bone-forming cells.
- Inside each epiphysis is spongy bone.
= a latticework of hard, strong trabeculae, composed of calcium minerals and living cells,
the spaces between the trabeculae are filled with red bone marrow (stem cells BCs)
- Compact bone: (figure 5.1!)
Made up of calcium phosphate enclosing and surrounding living cells, called
osteocytes, arranged in rings called osteons;
Blood vessels pass through a central canal (Haversian canal);
Osteocytes are trapped in lacunae, but remain in contact with each other via
canaliculi.
- Spongy bone:
thanks to the trabecular structure, each osteocyte has access to nearby blood vessels.
Ligaments hold bones together
Ligaments attach bone to bone, consist of dense fibrous connective tissue. Ligaments confer
strength to joints, while till permitting movement of the bones.
Cartilage lends support
Cartilage contains fibers of collagen and/or elastin in a ground substance of water and other
materials. It is smoother and more flexible than bone.
- Fibrocartilage: primarily collagen, withstands both pressure and tension well;
- Hyaline cartilage: smooth, of thin collagen fibers, covers the ends of bones in joints;
- Elastic cartilage: mostly elastin fibers, so highly flexible (ear and epiglottis).
Recap
Bones contribute to support, movement and protection. Bones also produce the blood cells and
store minerals. Ligaments hold bones together and cartilage provides support.
24

5.2 BONE DEVELOPMENT BEGINS IN THE EMBRYO
Chondroblasts
= cartilage-forming cells.
- Ossification = chondroblasts die out and the cartilage models dissolve and are replaced
by bone.
- After the chondroblasts die, the cartilage models break down, making room for blood
vessels to develop. The blood vessels carry bone-forming cells, called osteoblasts.
Osteoblasts
- secrete a mixture of proteins called osteoid, which forms a matrix that provides internal
structure and strength to bone,
- secrete enzymes that facilitate the crystallization of hard minerals (hydroxyapatite)
osteoblast become embedded in the hardening bone tissue.
- Mature osteoblasts continue to maintain the bone matrix.
Growth plate
= a narrow strip of cartilage remains in each epiphysis (during childhood).
- Chondroblast activity is concentrated on the outside of the plate,
- Conversion of cartilage to bone by osteoblast is concentrated on the inside of the plate.
Recap
Bone-forming cells called osteoblasts produce a protein mixture (including collagen) that becomes
bone’s structural framework. They also secrete an enzyme that facilitates mineral deposition.
5.3 MATURE BONE UNDERGOES REMODELING AND REPAIR
Osteoclast
Osteoclasts cut through mature bone tissue dissolving the hydroxyapatite and digesting the
osteoid matrix in their path. The released calcium and phosphate ions enter the blood. The areas
from which bone has been removed attract new osteoblasts, which lay down new osteoid
matrices and stimulate the deposition of new hydroxyapatite crystals.
Bones can change in shape, size and strength
Compression stress on a bone, causes tiny electrical currents within the bone, these stimulate
the bone-forming activity of osteoblasts.
Osteoporosis = condition in which bones lose a great deal of mass because of an imbalance in
the rates of activities of osteoclasts and osteoblasts.
Bone cells are regulated by hormones
- Calcium levels fall Parathyroid hormone (PTH)
stimulates osteoclasts to secrete more bone-dissolving enzymes;
- Calcium levels rise Calcitonin
stimulates osteoblast activity.
Bones undergo repair
- Hematoma
= a mass of clotted blood;
- Callus
= a fibrocartilage bond between the two broken ends of the bone.
25

Recap
Healthy bone replacement and remodeling depend on the balance of activities of bone-resorbing
osteoclasts and bone-forming osteoblasts. When a bone breaks, a fibrocartilage callus forms
between the broken ends and is later replaced with bone.
5.4 THE SKELETON PROTECTS, SUPPORTS AND PERMITS MOVEMENT
Types of bones
The axial skeleton forms the midline of the body
- The skull: Cranial and facial bones
- The vertebral column: The body’s main axis
- The ribs and sternum: Protecting the chest cavity
The appendicular skeleton: Pectoral girdle, pelvic girdle and limbs
- The pectoral girdle lends flexibility to the upper limbs
- The pelvic girdle supports the body
Read in book! Figures! (p. 110-114)
Recap
The skull and vertebral column protect the brain and spinal cord, the rib cage protects the organs of
the chest cavity and the pelvic girdle supports the body’s weight and protects the pelvic organs. The
upper limbs are capable of a wide range of motions (dexterous movement). The lower limbs are
stronger but less dexterous than the upper limbs.
5.5 JOINTS FORM CONNECTIONS BETWEEN BONES
5.6 DISEASES AND DISORDERS OF THE SKELETAL SYSTEM
Sprains mean damage to ligaments
Stretched or torn ligaments, often accompanied by internal bleeding (bruising, swelling, pain).
Bursitis and tendinitis are caused by inflammation
Inflammation of the tendons.
Arthritis is inflammation of joints
Osteoarthritis = most common, degenerative condition:
the cartilage covering the ends of the bones wears out, restricting joint movement.
Rheumatoid arthritis = caused by the body’s own immune system!
Osteoporosis is caused by excessive bone loss
Osteoporosis = condition caused by excessive bone loss, leading to brittle, easily broken bones.
26

6 THE MUSCULAR SYSTEM
6.1 MUSCLES PRODUCE MOVEMENT ORE GENERATE TENSION (FIGURE 6.3 - 6.4 -6.5!)
The fundamental activity of muscle is contraction
- Muscles are excitable;
- Muscles contract and relax.
Skeletal muscles cause bones to move
- Synergistic muscles antagonistic muscles;
- Origin and insertion.
A muscle is composed of many muscle cells
- Muscle
= group of muscle cells, with the same origin and insertion and the same function.
arranged in bundles, fascicles, enclosed in fibrous connective tissue (fascia).
- Each fascicle contains muscle fibers (=individual cells).
- At the end of the muscle, all of the fasciae come together, forming the tendons.
- Each individual cells is packed with long cylindrical structures arranged in parallel, called
myofibrils. The myofibrils are packed with proteins called actin and myosin.
The contractile unit is a sarcomere
- Sacromere
=a segment of a myofibril from one Z-line to the next,
consists of filaments composed of myosin and other filaments composed of actin.
- The actin filaments are linked to the Z-line.s
Recap
Muscles either produce or resist movement. Their fundamental activity is contraction. A muscle is
composed of many muscle cells arranged in parallel, each containing numerous myofibrils. The
contractile unit in a myofibril is called a sarcomere. A sarcomere contains thick filaments of a protein
called myosin and thin filaments of a protein called actin.
6.2 INDIVIDUAL MUSCLE CELLS CONTRACT AND RELAX
6.3 THE ACTIVITY OF MUSCLES CAN VARY
6.4 CARDIAC AND SMOOTH MUSCLES HAVE SPECIAL FEATURES
How cardiac and smooth muscles are activated
Speed and sustainability of contraction
Arrangement of myosin and actin filaments
striated muscle
p. 139 table 6.3!
Recap
Unlike skeletal muscle both cardiac and smooth muscle can contract in the absence of nerve
stimulation. Cardiac muscle contracts and then relaxes in a rhythmic cycle. Smooth muscle can
sustain a contraction indefinitely without ever relaxing.
6.5 DISEASES AND DISORDERS OF THE MUSCULAR SYSTEM
27

7 BLOOD
7.1 THE COMPONENTS AND FUNCTIONS OF BLOOD
Blood carries out three tasks:
• transportation;
• regulation;
• defense.
crucial for maintaining homeostasis.
Plasma consists of water and dissolved solutes
= water, dissolved proteins, hormones, different small molecules and ions.
Proteins:
- Albumins
serve to maintain the proper water balance between blood and the interstitial fluid,
also bind to certain molecules and drugs assisting in their transport in blood.
- Globulins
transport various substances in the blood;
• Alpha globulins,
• Beta globulins, bind to lipid molecules lipoprotein;
• Gamma globulins, function as a part of the immune system.
- Clotting proteins (see 7.2 Hemostasis)
Red blood cells transport oxygen and carbon dioxide
= erythrocytes, function primarily as carriers of oxygen and carbon dioxide
- RBCs = bags of plasma membrane, crammed with 300 million hemoglobin molecules:
- Hemoglobin
= oxygen-binding protein,
consists of 4 polypeptide chains, each containing a heme group:
at the end an iron atom forms a bond with oxygen molecules! (+ 4O 2 = oxyhemoglobin)
1,2 million molecules of oxygen bind to one RBC
Hematocrit and hemoglobin reflex oxygen-carrying capacity
- Hematocrit = percentage of blood that consists of RBCs,
= a relative measure of oxygen-carrying capacity ( 40%)
- Amount of hemoglobin
expressed in units of grams per 100 ml of blood (12-18%)
Low hematocrit Anemia? Other disorders?
High hematocrit Polycythemia? (overproduction of RBCs)
All blood cells and platelets originate from stem cells
Stem cells in the bone marrow, divide repeatedly, producing immature blood cells.
These blood cells develop into platelets and mature RBCs and WBCs. (Figure 7.5)
28

RBCs have a short life span
Erythroblasts fill with hemoglobin mature RBCs.
Old and damaged RBCs are removed from the circulating blood and destroyed in the liver and
spleen by macrophages (derived from monocytes, WBCs) in phagocytosis.
(Macrophages surround, engulf and digest the RBC)
Iron atoms are returned to the red bone marrow and used again.
Heme groups are converted to a pigment called bilirubin (when the liver fails: jaundice)
RBC production is regulated by a hormone
Regulation of RBC production = negative feedback control loop that maintains homeostasis.
- Erythropoietin
=hormone, secreted by the kidneys, that stimulates RBC production.
blood doping (dangerous: more RBC = more viscous blood!)
White blood cells defend the body
Granules = vesicles, visible when stained or not?
- Granular leukocytes
• Neutrophils
first WBCs to react to an infection, surround and engulf foreign cells,
especially bacteria and some fungi.
• Eosinophils
defend the body against large parasites, bombard it with digestive enzymes,
release chemicals that moderate the severity of allergic reactions.
• Basophils
secrete histamine, causing adjacent blood vessels to release blood plasma into
the injured area swelling, redness, warmth.
- Agranular leukocytes
• Monocytes
filter out of the blood into body tissues, then differentiate into macrophages that
engulf foreign particles and dead cellular debris by phagocytosis,
stimulate lymphocytes.
• Lymphocytes
B lymphocytes: give rise to plasma cells that produce antibodies,
T lymphocytes: target and destroy specific threats.
Platelets are essential for blood clotting
Platelets are small pieces of megakaryocyte cytoplasm and cell membrane (= not living cells,
megakaryocytes remain in the bone marrow).
Platelets participate in the clotting process.
Recap
Blood consists of a watery fluid containing cells, proteins, nutrients, cellular waste products and ions.
Red blood cells are specialized for transporting oxygen and carbon dioxide; white blood cells protect
against disease. Blood cells arise from stem in bone marrow. Platelets, important in blood clotting,
are small pieces of bone marrow cells called megakaryocytes.
29

7.2 HEMOSTASIS: STOPPING BLOOD LOSS
Vascular spasms constrict blood vessels to reduce blood flow
- Smooth muscle in the vessel wall undergoes spasms. This reduces immediate outflow of
blood or (in small vessels) stop the bleeding entirely, minimizing the damage.
Platelets stick together to seal a ruptured vessel
- When the lining of a blood vessel breaks, it exposes underlying proteins which cause the
platelets to swell, develop spiky extensions and begin to clump together.
The platelets start adhering to the walls of the vessel and to each other, the result is a
platelet plug which seals the injured area.
A blood clot forms around the platelet plug
- The blood changes from a liquid to a gel while forming a blood clot.
Three clotting factors:
• Prothrombin activator activates the conversion of prothrombin (plasma protein)
to an enzyme:
• Thrombin facilitates the conversion of a plasma protein fibrinogen into longer
threads of a protein:
• Fibrin threads wind around the platelet plug, forming an interlocking net of fibers
that trap and hold platelets, blood cells and various molecules against the
opening.
reduces the flow of blood at the site of injury.
- Hemophilia
= condition caused by a deficiency in one or more clotting factors.
Recap
Damage to blood vessels causes the vessels to spasm (contract). Nearby platelets become sticky and
adhere to each other limiting blood loss. In addition, a series of chemical events causes the blood in
the area to clot, or coagulate (form a gel).
30

7.3 HUMAN BLOOD TYPES
Blood type, based on ABO typing, based on antigen (= proteins on the outer surface of a cell).
ABO blood typing is based on A and B antigens
- Figure 7.12!
- No antigen antibodies that react to the antigens!
- Transfusion reaction:
• Antibodies attack RBCs with foreign antigens, damaging them and causing them
to agglutinate. If agglutination is extreme, clumps may block blood vessels.
• Damaged RBCs release hemoglobin, which can block the kidneys.
Rh blood typing is based on Rh factor
- Rh factor = a surface protein, + if you have it, - if you don’t.
- Hemolytic disease of the newborn:
Antibodies in a pregnant woman attack the blood of the fetus.
Blood typing and cross-matching ensure blood compatibility
- AB+ = universal recipients; O- = universal donors.
Recap
Blood types A, B, AB and O are defined by the presence of type A and/or B surface antigens on red
blood cells. In addition to the blood type, all persons are classified according to the presence of
another red blood cell surface antigen called the Rhesus factor. Antibodies to the Rh factor can cause
a serious immune reaction of a mother to her own fetus under certain circumstances.
7.4 BLOOD DISORDERS
Blood poisoning: Infection of blood plasma
= septicemia/toxemia,
caused by microorganisms in the blood, overwhelming its defenses and multiplying.
Symptoms: flushed skin, chills and fever, rapid heartbeat or shallow breathing.
Mononucleosis: Contagious viral infection of lymphocytes
= contagious infection of the lymphocytes and lymph tissues, caused by the Epstein-Barr virus.
Symptoms: flu (fever, headache, sore throat, fatigue, swollen tonsils and lymph nodes).
Anemia: reduction in blood’s oxygen-carrying capacity
Symptoms: pale skin, headaches, fatigue, dizziness, difficulty breathing, heart palpitations.
- Iron-deficiency anemia
hemoglobin cannot be synthesized properly decreased ability to transport oxygen;
- Hemorrhagic anemia
due to blood loss;
- Pernicious anemia
caused by a deficiency of vitamin B 12 absorption RBCs can’t function normally;
- Hemolytic anemia
result of a rupture or destruction of RBCs.
e.g. sickle-cell disease
(RBCs take on an abnormal shape in which oxygen concentration is low. Because of their
shape, they get damaged as they travel through small blood vessels and are destroyed by
the body.)
31

Leukemia: Uncontrolled production of white blood cells
= blood cancer,
overproduction of abnormal WBCs crowds out the production of normal RBC, WBC and platelets.
Symptoms: easy bruising, tender bones, sometimes headache or enlarged lymph nodes.
Multiple myeloma: Uncontrolled production of plasma cells
= type of cancer,
abnormal plasma cells in the bone marrow undergo uncontrolled division.
manufacture too much of an abnormal, incomplete antibody, impairing production of normal
antibodies and leaving the body vulnerable to infections.
Thrombocytopenia: Reduction in platelet number
= reduction in the number of platelets,
caused by viral infections, anemia, leukemia, other blood disorders, exposure to X-rays or
radiation, reaction to certain drugs...
Symptoms: easy bruising or bleeding, nosebleeds, bleeding in the mouth, blood in urine.
Recap
Blood poisoning and mononucleosis are types of blood infection. Several factors, including iron
deficiency or hemorrhage, can lead to a reduction in oxygen-carrying capacity of blood. Leukemia
and multiple myeloma are blood cell cancers that arise when abnormal cells in the bone marrow
divide uncontrollably. Thrombocytopenia, a disease of too few platelets, is characterized by easy
bleeding or bruising.
32

8 HEART AND BLOOD VESSELS
8.1 BLOOD VESSELS TRANSPORT BLOOD
Arteries transport blood away from the heart
- Arteries
Three layers:
• Endothelium: flattened squamous epithelial cells,
• Middle layer: smooth muscle, with interwoven elastic connective tissue,
• Outer layer: tough supportive layer of connective tissue, primarily collagen.
- Aneurysm
= ballooning of the artery wall, caused by damage to the endothelium, blood seeping
between the two outer layers.
Arterioles and precapillary sphincters regulate blood flow
- Arterioles
= smallest arteries, regulate the amount of blood flowing to each capillary by contracting
or relaxing the smooth muscle layer, altering the diameter of the arteriole lumen.
- Precapillary sphincter
= band of smooth muscle, “gates” that control blood flow into individual capillaries.
- Vasoconstriction:
contraction reduced diameter, reduce in blood flow to the capillaries;
Vasodilation:
relaxation increased diameter, increase in blood flow to the capillaries.
Capillaries: Where blood exchanges substances with tissues
- Capillaries
= the smallest blood vessels, with thin walls.
- Capillary beds = networks of capillaries.
- Only blood vessels that can exchange material with the interstitial fluid!
Lymphatic system helps maintain blood volume
Lymphatic capillaries,
pick up excess plasma fluid and other objects too large to diffuse into capillaries.
They transport the fluid, lymph, back to the veins near the heart via larger lymphatic vessels.
Veins return blood to the heart
Venules and veins return the blood to the heart. Three mechanisms assist them:
- Skeletal muscles squeeze veins
As the muscles contract and relax, they push the blood toward the heart;
- One-way valves permit only one-way blood flow
The structure of the valves allows blood to only flow toward the heart, it cannot fall back.
“skeletal muscle pumps”
- Pressures associated with breathing push blood toward the heart
Pressure changes in the thoracic and abdominal cavities during breathing:
push blood from the abdomen into the chest “respiratory pump”
33

Recap
A branching system of thick-walled arteries distributes blood to every area of the body. Arterioles
regulate blood flow to local regions and precapillary sphincters regulate flow into individual
capillaries. Capillaries consisting of a single layer of cells exchange materials with the interstitial fluid.
The lymphatic system removes excess fluid. The thin-walled veins return blood to the heart and serve
as a volume reservoir for blood.
8.2 THE HEART PUMPS BLOOD THROUGH THE VESSELS
The heart is mostly muscle
The heart has four chambers and four valves
figure 8.7 and 8.10!
The pulmonary circuit provides for gas exchange
Deoxygenated blood goes from the heart to the lungs via the pulmonary trunk and oxygenated
blood flows back to the heart.
The systemic circuit serves the rest of the body
Oxygenated blood leaves the heart via the aorta and serves the rest of the body
figure 8.8 and 8.9!
Coronary arteries supply the heart muscle,
cardiac veins collect the blood from the capillaries and channel it back to the right atrium.
The cardiac cycle: The heart contracts and relaxes
- Atrial systole
atria contract, pushing blood to the ventricles,
AV valves are open, semilunar valves are closed;
- Ventricular systole
ventricles contract, pushing blood to the pulmonary trunk and aorta,
AV valves close, semilunar valves open;
- Diastole
both relax, AV valves are open, semilunar valves are closed.
(figure 8.11)
Heart sounds reflect closing heart valves
Murmurs = unusual heart sounds.
Cardiac conduction system coordinates contraction
- Sinoatrial node
= small mass of cardiac muscle cells, near the junction of the right atrium and the
superior vena cava,
emits an electrical impulse that travels across both atria, stimulating contractions.
= cardiac pacemaker.
- Atrioventricular node
= located between the atria and ventricles, cause a slight delay
atria can contract and empty their blood into the ventricles, before the ventricles
contract
34

- Atrioventricular bundle
= group of conducting fibers in the septum between the two ventricles,
branch and extend into the Purkinje fibers.
- Purkinje fibers
= smaller fibers that carry the impulse to all the cells in the myocardium of the ventricles.
figure 8.13!
Electrocardiogram records the heart’s electrical activity
= record of the electrical impulses in the cardiac conduction system.
Recap
The heart wall consists of three layers; the epicardium, the myocardium and the endocardium. The
heart contains four chambers and four one-way valves. The right atrium and right ventricle pump
blood to the lungs, the left atrium and left ventricle pump blood to the rest of the body. Each cardiac
cycle is a repetitive sequence of contraction (systole) and relaxation (diastole). Contraction of the
heart is coordinated by modified cardiac muscle cells that initiate and transmit electrical impulses
through a specialized conduction system. An electrocardiogram is a recording of the heart’s electrical
activity taken from the surface of the body.
8.3 BLOOD EXERTS PRESSURE AGAINST VESSEL WALLS
Blood pressure
= the force that blood exerts on the wall of a blood vessel as a result of the pumping action of the
heart.
- Systolic pressure
= highest pressure, during ventricular systole,
- Diastolic pressure
= lowest pressure, during ventricular diastole.
Measuring blood pressure
Sphygmomanometer measures systolic and diastolic pressure:
mm Hg (millimeters of mercury)

8.4 HOW THE CARDIOVASCULAR SYSTEM IS REGULATED
Baroreceptors maintain arterial blood pressure
- Baroreceptors
= certain regions in large arteries that regulate arterial blood pressure:
• When blood pressure rises, blood vessels are stretched;
• Stretch of baroreceptors causes them to send signals to the cardiovascular
center in the brain;
• The cardiovascular center sends signals to the heart and blood vessels;
• The effect on the heart is to lower heart rate and the force of contraction
reduces cardiac output
(= amount of blood the heart pumps into the aorta each minute);
• The effect on the arterioles is vasodilation
increases blood flow through all tissues;
• Reduced cardiac output and increased flow through the tissues returns arterial
pressure to normal.
Nerves and hormones adjust cardiac output
- Medulla oblongata regulates cardiac output:
• Heart rate (number of heart beats per minute);
• Stroke volume (volume of blood pumped out with each heartbeat).
HR x SV = Cardiac output: 75 x 71ml = 5.25 liters per minute (=normal)
- Sympathetic nerves stimulate the heart,
parasympathetic nerves inhibit the heart.
- Epinephrine (adrenaline) and norepinephrine stimulate the heart,
secreted by the adrenal glands.
Local requirements dictate local blood flows
When metabolic activity of an organ increases, blood flow to that organ increases.
Exercise: Increased blood flow and cardiac output
Metabolic activity of the active skeletal muscles goes up dramatically
dilation of the blood vessels
(production of vasodilator waste products increases, local concentration of oxygen falls)
Recap
Homeostatic regulation of the cardiovascular system centers on maintaining a relatively constant
arterial blood pressure. Arterial pressure is sensed by baroceptors located in the carotid arteries and
aorta. Two opposing sets of nerves (sympathetic and parasympathetic) and a hormone (epinephrine)
adjust cardiac output and arteriole diameters to maintain arterial blood flow into individual
capillaries by altering the diameters of precapillary sphincters.
36

8.5 CARDIOVASCULAR DISORDER: A MAJOR HEALTH ISSUE
Angina: Chest pain warns of impaired blood flow
- Angina = sensation of pain and tightness in the chest, often accompanied by shortness of
breath and a sensation of choking or suffocating,
caused by impaired blood flow to the heart (e.g. narrowed coronary arteries).
- Angiography = procedure that enabled blood vessels to be visualized after they are filled
with a contrast medium angiograms.
Heart attack: Permanent damage to heart tissue
- Impaired blood flow for a long time
permanent damage to heart tissue, due to oxygen starvation
= heart attack = myocardial infarction.
Heart failure: The heart becomes less efficient
- If the heart muscle becomes damaged for any reason, the heart may become weaker and
less efficient at pumping blood.
- Congestive heart failure
= when too much fluid is filtered out of the capillaries and into the interstitial space,
causing fluid congestion.
Embolism: blockage of a blood vessel
- Embolism
= sudden blockage of a blood vessel by material floating in the bloodstream (embolus)
• Pulmonary embolism (artery supplying blood to the lungs);
• Cerebral embolism (artery supplying blood to the brain);
• Cardiac embolism (artery supplying blood to the heart).
Stroke: Damage to blood vessels in the brain
- Cerebrovascular accident (stroke)
= impairment of blood flow causes damage to brain cells.
( heart attack of the brain)
Recap
Cardiovascular disorders are the number one killer in the US. Most disorders are caused either by
conditions that result in failure of the heart as a pump or by conditions in which damage to blod
vessels restricts flow or ruptures vessels.
8.6 REDUCING YOUR RISK OF CARDIOVASCULAR DISEASE
Recap
You can reduce your risk of developing cardiovascular disease by not smoking, exercising regularly,
watching your weight and cholesterol and avoiding prolonged stress. If you have diabetes and/or
hypertension, try to keep these conditions under control.
37

9 THE IMMUNE SYSTEM AND MECHANISMS OF DEFENSE
9.1 PATHOGENS CAUSE DISEASE
Bacteria: Single-celled living organisms
= single-celled organisms without nucleus or membrane-bound organelles.
The DNA is contained in just one chromosome. Bacteria use ATP for energy and amino acids for
making proteins.
They obtain raw materials from their environment (soil and air, dead animals and plants).
treated with antibiotics.
Viruses: Tiny infectious agents
= small infectious agents with a very simple structure. Consists of a small piece of genetic
material, surrounded by a protein coat.
Prions: Infectious proteins
= misfolded form of a normal brain cell protein, which can trigger the misfolding of nearby
normal forms of the protein.
Eventually so many prions accumulate within infected brain cells that the cells die and burst,
releasing prions to infect other cells.
Transmissibility, mode of transmission and virulence determine health risk
= how easily it is passed from one person to another;
= how it is transmitted;
= how damaging the resulting disease is.
Recap
Like all cells, bacteria draw their energy and raw materials from their environment. Pathogenic
bacteria get the materials they need from living cells, damaging or killing the cells in the process. A
virus consists of a single strand of DNA or RNA surrounded by a protein. Viruses use their DNA or
RNA to force a living cell to make more copies of the virus. Prions are infectious proteins that cause
normal proteins to misfold.
9.2 THE LYMPHATIC SYSTEM DEFENDS THE BODY
Three important functions:
• maintain the volume of blood;
• transport fats and fat-soluble vitamins to the cardiovascular system;
• defend the body against infection.
Lymphatic vessels transport lymph
Lymphatic capillaries form a network, they can take up substances that are too large to enter a
blood capillary. Lymph is the fluid which fills these capillaries. It contains white blood cells,
proteins, fats and bacteria and viruses.
Lymphatic capillaries merge to form the lymphatic vessels. Their walls consist of three layers and
they contain one-way valves to prevent backflow of lymph.
Lymphatic vessels merge to form two major lymphatic ducts: the right lymphatic duct and the
thoracic duct.
The lymphatic ducts connect to the cardiovascular system by joining the subclavian veins near
the shoulders.
38

Lymph nodes cleanse the lymph
Lymph nodes remove microorganisms, cellular debris and abnormal cells from the lymph. Each
node is enclosed in a dense capsule of connective tissue pierced by lymphatic vessels.
Inside macrophages and lymphocytes (WBCs) identify microorganisms and remove them.
Macrophages destroy foreign cells by phagocytosis, lymphocytes activate other defense
mechanisms. Valves within the lymphatic vessels ensure that lymph flows only in one direction.
The spleen cleanses blood
= soft, fist-sized mass located in the left abdominal cavity. Covered with a dense capsule of
connective tissue interspersed with smooth muscles cells. Inside the organ are two types of
tissue, called red pulp and white pulp.
The spleen has two main functions:
- Control the quality of the circulating RBCs by removing the old and damaged ones;
- Fight infections.
The red pulp contains macrophages that scavenge and break down microorganisms and old or
damaged RBCs&platelets. The cleansed blood is then stored in the red pulp (reserve).
The white pulp contains primarily lymphocytes searching for foreign pathogens. The white pulp
does not store blood.
Thymus gland hormones cause T lymphocytes to mature
= located in the lower neck, encased in connective tissue. It contains lymphocytes and epithelial
cells.
The thymus gland secretes two hormones, thymosin and thymopoietin, that cause T lymphocytes
to mature. The thymus gland is largest and most active during childhood and stops growing
(starts shrinking) after adolescence. It may disappear entirely in old age.
Tonsils protect the throat
= masses of lymphatic tissue near the throat.
Lymphocytes gather and filter out many of the microorganisms that enter the throat.
We have several tonsils, e.g. the adenoids. The adenoids tend to enlarge during childhood, but
mostly start to shrink by the age of 5 and disappear by puberty.
They can be surgically removed if they grow large enough to cause trouble.
Recap
The lymphatic system helps protect us from disease. Macrophages and lymphocytes within the
lymph nodes identify microorganisms and remove them. The spleen removes damaged red blood
cells and foreign cells from blood. The thymus gland secretes hormones that help T cells mature.
Cells in the tonsils gather and remove microorganisms that enter the throat.
39

9.3 KEEPING PATHOGENS OUT: THE FIRST LINE OF DEFENSE
Skin: An effective deterrent
The skin has 4 attributes that make it an effective barrier:
- Its structure;
Keratin:
forms a dry, though, somewhat elastic barrier to the entry of microorganisms,
after cells have died and water has evaporated.
- The fact that it’s constantly being replaced;
Dead cells shed from the surface and are replaced by new cells at the base of the
epidermis. Those dead cells protect from pathogens that are deposited on the surface.
- Its acidic pH;
(because of sweat) This makes skin a hostile environment for many microorganisms.
- The production of an antibiotic by sweat glands.
Dermicidin = a natural antibiotic peptide, that can kill a range of harmful bacteria.
Impeding pathogen entry in areas not covered by skin
- Tears, saliva and earwax
Tears lubricate the eyes and wash away particles.
Tears & saliva contain lysosome, en enzyme that kills many bacteria.
Saliva lubricates the delicate tissues inside the mouth and
rinses microorganisms from the mouth to the stomach.
Earwax traps small particles and microorganisms.
- Mucus
= thick, gel-like material secreted by cells at various surfaces of the body.
Microorganisms become mired and cannot gain access to underlying cells.
The cells of the airways have cilia, that sweep mucus upward into the throat, to get rid of
it we cough, swallow or sneeze.
- Digestive and vaginal acids
Digestive acid is strong enough to kill nearly all pathogens that enter the digestive tract.
Only helicobacter pylori, a strain of bacteria, can survive.
Vaginal acid is not nearly as acidic as stomach secretions.
- Vomiting, urination and defecation
Vomiting is an effective way of getting rid of toxic or infected stomach contents.
The acidity of the urine inhibits bacterial growth and urine flushes the bacteria out.
Movement of feces and defecation help remove microorganisms from the digestive tract.
(Mild cases of diarrhea speeds the removal of pathogens)
- Resident bacteria
“Good” bacteria compete successfully against “bad” bacteria for food, so the “bad”
bacteriapopulation cannot grow.
Recap
Various mechanisms create an inhospitable environment for pathogenic microorganisms. Skin is a
dry outer barrier. Tears, saliva, earwax and mucus trap pathogens or wash them away. Acidic
conditions kill them or inhibit their growth; urination, defecation and vomiting forcibly expel them
and resident bacteria compete with pathogens for food.
40

9.4 NONSPECIFIC DEFENSE: THE SECOND LINE OF DEFENSE
Phagocytes engulf foreign cells
- Phagocytosis (phagocytes ‘eat’ the pathogen)
The phagocytes first captures the pathogen, then draws it in – engulfing it – and
enclosing it in a membrane-bound vesicle (endocytosis). Inside the cells, that vesicle
fuses with lysosomes and the enzymes in those dissolve the bacterial membranes. Once
digestion is complete, the phagocyte jettisons the bacterial wastes by exocytosis.
- Neutrophils
= first WBCs to respond to infection, destroy bacteria in the blood and tissue fluid;
- Monocytes enter tissue fluids and develop into macrophages
engulf/digest large numbers of foreign cells, especially viruses and bacterial parasites,
they serve a clean-up function by scavenging old BCs, dead tissue and cellular debris.
They also release chemicals that stimulate the production of more WBCs.
- Eosinophils
cluster around large parasites and bombard them with digestive enzymes, also engulf
and digest certain foreign proteins.
- Tissue fluid, dead phagocytes and microorganisms and cellular debris from pus.
When pus is trapped and cannot drain the body may was it off with connective tissue
forming an abscess.
Inflammation: Redness, warmth, swelling and pain
Inflammatory response starts whenever tissues are injured.
- Release of chemicals from the damaged cells;
- These chemicals stimulate mast cells (specialized to release histamine), basophils
(WBCs) also secrete histamine;
- Histamine promotes vasodilation of neighboring small blood vessels.
the endothelial cells in the vessel walls pull slightly apart and the vessels become more
permeable: WBCs can pass through.
- Phagocytes pass through capillary walls into the interstitial fluid, here they attack foreign
organisms and damaged cells.
(Some travel to the lymphatic system, which activates the lymphocytes to initiate specific
defense).
- Symptoms explained:
Vasodilation brings more blood to the injured area red and warm. Rising temperature
increases phagocyte activity.
Increased permeability of vessels, allows more fluid into tissue spaces swelling.
Swollen tissues press against nearby endings pain.
Natural killer cells target tumors and virus-infected cells
= group of WBCs that destroy tumor cells and virus-infected cells. They are able to recognize
changes that take place in the plasma membranes of tumor/infected cells.
They release chemicals that break down their targets’ cell membranes.
They also secrete substances that enhance the inflammatory response.
41

The complement system assists other defense mechanisms
= 20 plasma proteins that circulate in the blood, assist other mechanisms.
Some join to form large protein complexes that create holes in bacterial cell walls, then fluids
and salts leak in until it bursts.
Others bind to bacterial cell membranes, marking them for destruction by phagocytes.
Others stimulate mast cells to release histamine, or serve as chemical attractants to draw
additional phagocytes to the infection.
Interferons interfere with viral reproduction
= group of proteins, diffuse to nearby healthy cells, bind to the cell membranes
and stimulate them to produce proteins that interfere with the synthesis of viral proteins,
making it harder for viruses to infect the protected cell.
Fever raises body temperature
Macrophages release certain chemicals called pyrogens, which cause the brain to raise body
temperature. Modest fever makes our internal environment less hospitable to pathogens and
enhances the body’s ability to fight infection. Fever increases the metabolic rate of body cells,
speeding up both defense mechanisms and tissue-repair processes.
Recap
Nonspecific defense mechanisms involve a general attack against all foreign and damaged cells.
Neutrophils and macrophages engulf and digest bacteria and damaged cells and eosinophils
bombard larger organisms with digestive enzymes. The inflammatory response attracts phagocytes
and promotes tissue healing. Interferons interfere with viral reproduction. Fever enhances our ability
to fight infections.
9.5 SPECIFIC DEFENSE MECHANISMS: THE THIRD LINE OF DEFENSE
Immune response:
1. Recognizes and targets specific pathogens or foreign substances;
2. Has a “memory”, the capability to store information from past exposures;
3. Protects the entire body; resulting immunity is not limited to the site of infection.
The immune system targets antigens
- Antigens
= proteins on the outer surface of a cell
= substance that mobilizes the immune system and provokes an immune response.
Body produces antibodies in reaction to antigens
- Major histocompatibility complex proteins (MHC-proteins)
= proteins on the outer surface that serve as ‘self markers’
42

Lymphocytes are central to specific defense
= white blood cells, originating from stem cells in the bone marrow
- B cells
(mature in Bone marrow)
= responsible for antibody-mediated immunity
produce antibodies, proteins that bind with and neutralize specific antigens
viruses, bacteria, foreign molecules soluble in blood and lymph
- T cells
(mature in Thymus gland)
= responsible for cell-mediated immunity
Some: directly attack foreign cells (that carry antigens);
Others: release proteins that help coordinate other aspects of the immune response
parasites, bacteria, viruses, fungi, cancerous cells, cells perceived as foreign
B cells: Antibody-mediated immunity
- As they mature, they develop unique surface receptors
allow them to recognize specific antigens.
- Travel to the lymph nodes, spleen and tonsils
remain inactive until they encounter a foreign cell with the specific antigen.
- Surface receptors bind to the antigen
activates the B cell to grow and multiply rapidly (clones)
- Different types of clones
• Plasma cells
= secrete their antibodies into the lymph and ultimately into the blood plasma.
Antibodies encounter matching antigens, bind to them and create
an antigen-antibody complex
(= marks the antigen for destruction by activated complement
proteins/phagocytes)
• Memory cells
= remain inactive until that same antigen reappears in the body,
store information about the pathogen.
long-term immunity
43

The five classes of antibodies
Antibodies = blood plasma proteins called gamma glubolins (often immunoglobulin Ig)
- IgG
found in blood, lymph, intestines and tissue fluids;
activate the complement system and neutralize many toxins.
Only antibodies that cross the placenta!
- IgM
found in blood and lymph;
activate tha complement system and cause foreign cells to agglutinate (e.g. ABO)
First to be released during immune responses!
- IgA
enter areas of the body covered by mucous membranes;
neutralize infectious pathogens.
Are present in mother’s milk!
- IgD
found in blood, lymph and B cells;
function not clear, role in activating B cells.
- IgE
found in B cells, mast cells and basophils;
activate the inflammatory response by triggering the release of histamine.
Reason for allergic responses!
Antibodies’ structure enables them to bind to specific antigens
- Antigens provide all the information the immune system needs.
- All antibodies share the same basic structure:
constant region (forms the trunk and two branches);
variable region (forms the antigen-binding site:
unique amino acid sequence: unique shape = specific antigen!)
T cells: Cell-mediated immunity
- Differences between B and T:
1. B produce circulating antibodies;
T releases chemicals that stimulate other cells, or attack the foreign cell directly;
2. B recognize antigens;
T can’t recognize whole antigens, they need it in a form they recognize (fragments)
- Antigen-presenting cells (APCs)
= cells (macrophages/activated B cells) that engulf foreign particles, partially digest them
and display fragments of the antigens on their surfaces
T cells react
44

- Different types of T cells: determined by a set of surface proteins:
• CD4 cells
become helper and memory cells:
‣ Helper T cells stimulate other immune cells
secrete cytokines (signaling molecules):
cytokines stimulate other immune cells such as phagocytes, natural killer
cells, T cells with CD8 receptors.
‣ Memory T cells reactivate during later exposures
retain receptors for the antigen,
when presented with it again, they reactivate (quicker than at first)
• CD8 cells
become cytotoxic and suppressor cells.
‣ Cytotoxic T cells kill abnormal and foreign cells
CD8 cells clone and directly attack and destroy the other cells
releases protein perforin
assemble into a pore in the target cell, allowing water and salts to enter,
this kills the cell.
releases granzyme (toxic enzyme) which passes through the pore
made by perforin.
Recap
An antigen is any substance that provokes an immune response. When activated by first exposure to
a specific antigen, lymphocytes called B cells quickly produce antibodies against the antigen. They
also produce a few long-lived memory cells that remain inactive until the next exposure to the same
antigen. Other lymphocytes called T cells mature in the thymus glans. Helper T cells stimulate other
immune cells, cytotoxic T cells attack abnormal and foreign cells and memory T cells store
information until the next exposure to the same antigen.
9.6 IMMUNE MEMORY CREATES IMMUNITY
First exposure
- Primary immune response:
(recognition of antigen, production and proliferation of T and B cells)
Has a lag time of 3-6 days.
- Secondary immune response:
faster, longer lasting and more effective.
(thanks to memory cells)
Immunity
Recap
First exposure to a specific antigen generates a primary immune response. Subsequent exposure to
the same antigen elicits a secondary immune response that is faster, longer lasting and more
effective than the primary immune response.
45

9.7 MEDICAL ASSISTANCE IN THE WAR AGAINST PATHOGENS
Active immunization: An effective weapon against pathogens
- Vaccine
= antigen-containing preparation
(made from dead or weakened pathogens)
- Limitations:
• Issues of safety, time and expense:
weakened cells elicit a greater immune response, but can cause disease;
• A vaccine confers immunity against only one pathogen;
• Vaccines are not effective after a pathogen has already struck.
- Nonetheless, an effective supplement!
Passive immunization can help against existing or anticipated infections
- Gama globulin shot
= prepared antibodies (saves time)
- Advantage:
• It is effective against an existing infection.
• However, protection is not as long-lasting as active immunization.
Antibiotics combat bacteria
- Antibiotics
kill bacteria or inhibit their growth; (e.g. penicillin)
- Work in different ways,
in general they take advantage of differences between bacteria and human cells:
• Bacteria have a thick cell wall, human cells do not;
• Bacterial DNA is not enclosed in a nucleus, human DNA is;
• Bacterial ribosomes are smaller than human ribosomes;
• Bacterial rate of protein synthesis is very rapid as they grow and divide.
- Broad-spectrum antibiotics
= effective against several groups of bacteria
- Ineffective against viruses.
Recap
Active immunization with a vaccine produces a primary immune response and readies the immune
system for a secondary immune response. Passive immunization (prepared antibodies) can be
effective against existing infections but does not confer log-term immunity. Most antibiotics kill
bacteria by interfering with bacterial protein synthesis or bacterial cell wall synthesis.
46

9.8 TISSUE REJECTION: A MEDICAL CHALLENGE
Tissue rejection
= immune system attacks foreign human tissue.
Transfusion reaction
= rejection of blood, can be fatal.
Transplantation:
- Search for a good match;
- Immunosuppressive drugs
block the immune response, after a transplantation.
Can prolong the lives of patients, but brings other risks!
Recap
The major obstacle to organ transplantation is the recipient’s immune response, as cytotoxic T cells
attack all foreign cells.
9.9 INAPPROPRIATE IMMUNE SYSTEM ACTIVITY CAUSES PROBLEMS
Allergies: A hypersensitive immune system
- Allergy
= inappropriate immune response to an allergen.
the allergen is not dangerous, but the body reacts as if it were:
inflammatory response!
- Some allergens affect only the areas exposed,
others are absorbed or injected into the bloodstream.
The later often elicit a systemic response, they affect several organ systems.
- Severe systemic allergic reaction:
• Difficulty breathing;
• Severe stomach cramps,
• Swelling throughout the body;
• Circulatory collapse, fall in blood pressure.
= anaphylactic shock
(solved by epinephrine: dilates airway and
constricts peripheral blood vessels, preventing shock)
9.10 IMMUNE DEFICIENCY: THE SPECIAL CASE OF AIDS
(only slides!)
47

10 THE RESPIRATORY SYSTEM
10.1 RESPIRATION TAKES PLACE THROUGHOUT THE BODY
Respiration encompasses four processes
- Breathing (or ventilation): movement of air into and out of the lungs;
- External respiration: exchange of gases between inhaled air and blood;
- Internal respiration: exchange of gases between blood and tissue fluids;
- Cellular respiration: process of using oxygen to produce ATP, with CO 2 as waste product.
10.2 THE RESPIRATORY SYSTEM CONSIST OF UPPER AND LOWER RESPIRATORY TRACTS
The respiratory system consist of upper and lower tracts
- Upper respiratory tract: nose and pharynx;
- Lower respiratory tract: larynx, trachea, bronchi and lungs.
The upper respiratory tract filters, warms and humidifies air
- Nose:
• Contains receptors for smell;
• Filters inhaled air and screens out foreign particles;
• Moistens and warms incoming air;
• Provides resonating chamber (voice).
- Cilia covers epithelium in nasal cavity.
- Mucus in nasal cavity traps dust, pathogens and other particles.
- Sinuses:
air spaces inside the skull, lined with tissue that secretes mucus.
- Pharynx: connects mouth and nasal cavity to the larynx;
upper pharynx: two auditory tubes open into it;
lower pharynx: common passageway for food and air.
The lower respiratory tract exchanges gases
- The larynx produces sound
• Larynx or voice box serves to maintain an open airway, rout food and air into the
right channels and assist in the production of sound.
• Epiglottis = flexible flap of cartilage which blocks the opening to the larynx when
swallowing.
• Vocal cords = to folds of connective tissue that extend across the airway,
surrounding the opening called the glottis.
produce sounds by vibration of air passing through.
- The trachea transports air
• Trachea consists of C-shaped, incomplete cartilage rings, held together by
connective tissue and smooth muscle;
• Lined with cilia-covered epithelial tissue that secretes mucus;
• Cough reflex: when smooth muscle contracts, the diameter of the trachea
reduces, so air comes through more fiercely and obstacles can be removed.
48

- Bronchi branch into the lungs
• Trachea branches into two bronchi as it enters the lung cavity;
• Bronchioles = smaller airways that lack cartilage.
• Several functions: clean the air, warm it, saturate it
by contact with moist surface of the cells lining the bronchi and bronchioles.
- The lungs are organs of gas exchange
• Two lungs, follow the contours of the rib cage and thoracic cavity,
each lung consist of several lobes (3 in the right, 2 in the left lung);
• Pleural membranes = two membranes (lines lungs/lines thoracic cavity) with fluid
in between (reduces friction).
- Gas exchange occurs in alveoli
• Alveolus = tiny air-filled sacs, cluster at the end of every terminal bronchiole, a
thin bubble of living squamous epithelial cells only one cell layer thick.
• Surfactant = certain cells produce a lipoprotein, that coats the interior of the
alveoli and reduces surface tension (otherwise alveoli would collapse).
- Pulmonary capillaries bring blood and air into close contact
• Blood in pulmonary capillaries is only two cell layers away from the air
(the squamous epithelial cell of the alveolus/the cell of the capillary wall)
exchange of oxygen and carbon dioxide to and from the blood;
brings medication quickly into the bloodstream.
Recap
The respiratory system is specialized for the exchange of oxygen and carbon dioxide with the air.
Sound is produces by vibration of the vocal cords of the larynx as air passes through the glottis. The
trachea branches into the right and left bronchi. The bronchi and bronchioles filter, warm and
humidify the incoming air. The lungs are organs containing a branching system of bronchi and
bronchioles, bloods vessels and 300 million alveoli. Gas exchange occurs between the alveoli and
pulmonary capillaries.
10.3 THE PROCESS OF BREATHING INVOLVES A PRESSURE GRADIENT
Intercostal muscles and diaphragm
= broad sheet of muscle that separates the thoracic cavity from the abdominal cavity.
Inspiration brings air, expiration expels it
- General principles of gas pressure and how gas moves
- Inspiration and expiration
1. Relaxed state
= both diaphragm and intercostal muscles are relaxed;
2. Inspiration
diaphragm and intercostal muscles contract lung volume increases, air flows in;
3. Expiration
diaphragm and intercostal muscles relax lung volume declines, air flows out.
Lung volumes and vita capacity measure lung function
- Tidal volume
= how much air a normal breath represents,
dead space volume = air inhaled which is not used for gas exchange.
49

- Vital capacity
inspiratory reserve volume = additional air that can be inhaled;
expiratory reserve volume = additional air that can forcibly exhaled;
residual volume = some air always remains in the lungs.
- Spirometer = measures lung capacity.
Recap
Inspiration is an active process that occurs when the diaphragm and intercostal muscles contract.
Normally expiration is passive but it can become active when we forcibly exhale, cough or sneeze.
Although we normally take breaths of about 500ml, the maximum breath we can inhale and then
forcibly exhale is about 4,800 ml. Some air, called the residual volume, remains in the lungs even at
the end of expiration.
10.4 GAS EXCHANGE AND TRANSPORT OCCUR PASSIVELY
Gases diffuse according to their partial pressures
External respiration: The exchange of gases between air and blood
Internal respiration: The exchange of gases with tissue fluids
Hemoglobin transports oxygen molecules
Most CO 2 is transported in plasma as bicarbonate
read in book (p. 229)
Recap
In a mixture of gases such as air, each gas exerts a partial pressures. Diffusion accounts for both
external and internal respiration. Nearly all of the oxygen in blood is bound to hemoglobin in RBCs.
Most carbon dioxide produced in the tissue is transported in blood plasma as bicarbonate.
10.5 THE NERVOUS SYSTEM REGULATES BREATHING
A respiratory center establishes rhythm of breathing
Chemical receptors monitor CO 2 , H+ and oxygen levels
We can exert some conscious control
read in book (p.233)
Recap
The respiratory center in the brain establishes a regular pattern of cyclic breathing. The rate and
depth of breathing are then adjusted by regulatory mechanisms that monitor arterial concentrations
of CO 2 , H+ and O 2 . Conscious control can modify regulatory control but cannot override it completely.
10.6 DISORDERS OF THE RESPIRATORY SYSTEM
Reduces air flow or gas exchange impedes respiratory function
- Asthma: Spasmodic contraction of bronchi
= characterized by spasmodic contraction of bronchi bronchial swelling an increased
production of mucus;
An asthma attack causes partial closure of the bronchi, making breathing difficult;
most attacked are caused by a hyperactive immune system, the body reacts to allergens
with excessive production of immunoglobulin
release of histamine etc. leading to inflammation and constriction of bronchiolar
smooth muscle.
50

- Emphysema: Alveoli become permanently impaired (don’t have to know it)
= chronic disorder involving damage to the alveoli;
It begins with destruction of connective tissue in the airways, as a result they become
less elastic do not stay open properly and tend to collapse during expiration. This causes
high pressure in the lungs which damages the fragile alveoli.
permanent reduction in the surface area available for diffusion, reduced lung capacity
- Bronchitis: Inflammation of the bronchi (don’t have to know it)
Can be acute or chronic, symptoms are wheezing breathlessness and a persistent cough
that yields yellowish or greenish phlegm.
- Cystic fibrosis: An inherited condition
= a single defective gene causes the mucus-producing cells to produce a thick, sticky
mucus, the disease affects other organs as wall.
The thick mucus impedes air flow and also provides a site for the growth of bacteria.
Microorganisms can cause respiratory disorders
- Colds and the flu: Common viral respiratory tract infections (don’t have to know it)
Caused by viruses, highly contagious but not very virulent.
Upper respiratory infection (cold):
symptoms: coughing, runny nose, nasal congestion and sneezing.
Flu: symptoms: sore throat, fever, cough,
sometimes aches and chills, muscle pains and headache.
- Pneumonia: Infection inflames the lungs (don’t have to know it)
= infection caused by viruses or bacteria.
Alveoli secrete excess fluid, impairing the exchange of oxygen and carbon dioxide.
Symptoms: fever, chills, shortness of breath and a cough that yields yellow-greenish
phlegm and sometimes blood.
- Tuberculosis: Bacterial infection scars the lungs
= infectious disease caused by the mycobacterium tuberculosis.
Disease spreads via lymphatic vessels and may enter the bloodstream.
Symptoms: coughing, chest pain, shortness of breath, fever, night sweats, loss of
appetite, weight loss.
tuberculin test.
- Botulism: Poisoning by bacterial toxin (don’t have to know it)
= form of poisoning caused by clostridium botulinum, found in improperly cooked or
preserved foods.
The bacterium produces a powerful toxin that blocks the transmission of nerve signals to
skeletal muscles, including the diaphragm and intercostal muscles.
Symptoms appear 8 to 36 hours after contamination:
difficulty swallowing and speaking, double vision, nausea, vomiting.
51

Lung cancer is caused by proliferation of abnormal cells (don’t have to know it)
= uncontrolled growth of abnormal cells. In the lungs, abnormal cells impede normal function:
movement of air in the lungs and/or exchange of gases in the alveoli.
strongly associated with smoking.
Symptoms: chronic cough, wheezing, chest pain, coughing up blood.
Pneumothorax and atalectasis: A failure of gas exchange (don’t have to know it)
Pneumothorax = collapse of one or more lobes of the lungs.
(Most common cause is a penetrating wound, that allows air into the pleural cavity.)
(wat Linnert had!)
Atalectasis = lack of gas exchange within the lung, as a result of alveolar collapse or a build-up of
fluid within alveoli.
both: no exchange of gases!
Congestive heart failure impairs lung function(don’t have to know it)
As a result of congestive heart failure, the blood backs up in the pulmonary blood vessels. The
result is a rise in blood pressure in the pulmonary vessels. Increased pressure causes fluid loss
from the capillary (physical pressure and osmotic forces change). As a result, fluid builds up in the
interstitial spaces between capillaries and alveoli (or alveoli themselves). This increases the
diffusional distance and reduces diffusion of gases.
Recap
The lungs are prone to damage by environmental pollutant, tobacco smoke and infections by
microorganisms. Cases of both asthma and tuberculosis are on the rise.
11 THE NERVOUS SYSTEM
12 SENSORY MECHANISMS
52

13 THE ENDOCRINE SYSTEM
13.1 THE ENDOCRINE SYSTEM PRODUCES HORMONES
Endocrine system
= a collection of specialized cells, tissues and glands that produce and secrete circulating chemical
messenger molecules called hormones.
Hormones are secreted by endocrine glands, ductless organs that secrete their products into
interstitial fluid, lymph and blood.
Exocrine glands secrete products into ducts that empty into the appropriate sites.
P. 303 fig. 13.1!!
1. Hormones of the endocrine system reach nearly every living cell.
2. Each hormone acts only on certain cells (target cells).
3. Endocrine control tends to be slower than nervous system control.
4. The endocrine and nervous system can interact with each other.
Recap
Hormones secreted by glands of the endocrine system act only on target cells with the appropriate
receptors. Hormones reach their targets via the circulatory system, making the endocrine system
control slower than nervous system control. The two systems frequently interact.
13.2 HORMONES ARE CLASSIFIED AS STEROID OR NONSTEROID
Steroid hormones, structurally related to cholesterol, lipid soluble.
Nonsteroid hormones, structurally related to proteins, lipid insoluble.
Steroid hormones enter target cells
- Can diffuse through the cell membrane and through the nuclear membrane.
- Inside the cell, they bind to specific receptors, forming a hormone-receptor complex,
either within the nucleus or within the cytoplasm.
- In the nucleus the complex attaches to DNA, activating specific genes.
Gene activation causes the formation of mRNA which then leaves the nucleus and
directs the synthesis of proteins.
Nonsteroid hormones bind to receptors on target cell membranes
- Cannot enter the cell.
- They bind to receptors on the outer surface of the cell membrane.
This causes a change in the shape of the receptor which in turn stimulates a change
within the cell itself.
- Some nonsteroid hormones cause ion channels to open or close,
other hormone-receptor bindings convert inactive molecules to active molecules
second messenger.
- The second messenger carries the message from the hormone within the cell.
e.g. cAMP.
- Nonsteroid hormones tend to be faster than steroid hormones.
53

Hormones participate in negative feedback loops
- In a negative feedback loop involving a hormone, the endocrine gland is the control
center.
- The hormone represents the pathway between the control center and the effectors.
- The effectors are the hormone’s target calls, tissues or organs.
Recap
Many hormones participate in negative feedback lops that maintain homeostasis. Steroid hormones
enter the target cell activate, specific genes and cause the production of new proteins. Non steroid
hormones bind to a cell membrane receptor that either opens or closes ion channels or activates a
second messenger within the cell.
13.3 THE HYPOTHALAMUS AND THE PITUITARY GLAND
Hypothalamus
= small region in the brain that serves as a homeostatic control center.
Pituitary gland (= hypofyse)
= secretes eight different hormones, that in turn regulate many of the other endocrine glands.
The posterior pituitary stores ADH and oxytocin
Neuroendocrine cells
= cells in the hypothalamus that function as both nerve cells and endocrine cells.
When the hypothalamus is stimulated to release hormones, the neuroendocrine cells send
impulses down the axon, causing hormones to be secreted into nearby capillaries.
- ADH regulates water balance
Antidiuretic hormone,
reduces the amount of water lost in urine.
• Primary target cells: in the kidneys: causes changes in cell permeability.
- Oxytocin causes uterine contractions and milk ejection
• Primary target cells: in the uterus and mammary glands.
stimulates contractions of the uterus during childbirth
and ejection of milk during suckling.
• Neuroendocrine reflex
= a nervous system stimulus is responsible for secretion of a hormone.
54

The anterior pituitary produces six key hormones
Each anterior pituitary hormone is produced and secreted by a separate cell type,
each hormone is regulated by separate mechanisms.
The anterior pituitary depends on the hypothalamus: endocrine connection.
- ACTH stimulates the adrenal cortex
Adrenocorticotropic.
• Target cells: located in the cortex of the adrenal gland.
stimulates the cortex to release glucocorticoids (= steroid hormones involved
in stress-related conditions and the control of glucose metabolism.)
- TSH acts on the thyroid gland
Thyroid-stimulating hormone,
stimulates the thyroid gland to synthesize and release thyroid hormones.
• TSH-releasing hormone from the hypothalamus.
- FSH and LH stimulate the reproductive organs
Follicle-stimulating hormone and luteinizing hormone = gonadotropins,
stimulate growth, development and function of the reproductive organs.
- Prolactin: Mammary glands and milk production
Stimulates the development of mammary gland cells and the production of milk.
• Prolactin-releasing hormone from the hypothalamus:
toward the end of pregnancy, hypothalamus stimulated by estrogen.
• Prolactin-inhibiting hormone from the hypothalamus,
when a woman is not in late pregnancy or breast-feeding.
- Growth hormone: Widespread effects on growth
influences cells in ways that promote growth.
Pituitary disorders: Hypersecretion or hyposecretion
- Diabetes insipidus
caused by hyposecretion of ADH, which causes the kidneys to lose too much water.
• Excessive urination, dehydration, thirst, headache, dry mouth.
- Pituitary dwarfism
caused by hyposecretion of growth hormone, in childhood.
- Pituitary gigantism
caused by hypersecretion of growth hormone, in childhood.
- Acromegaly
caused by excessive production of growth hormone in adults over long periods
• Gradual thickening of the bones in the face, hands and feet.
Recap
ADH acts on the kidneys to regulate water balance. Oxytocin stimulates uterine contraction and milk
ejection in pregnant and lactating females. In both sexes, oxytocin contributes to feelings of sexual
satisfaction. The six hormones produced by the anterior pituitary are ACTH,TSH, FSH, LH, prolactin
and GH. The release of each hormone is controlled in part by a releasing or inhibiting hormone from
the hypothalamus.
55

13.4 THE PANCREAS SECRETES GLUCAGON, INSULIN AND SOMATOSTATIN
Pancreas
= both an endocrine and exocrine gland.
Islets of Langerhans
= small clusters scattered throughout the pancreas, in which the endocrine cells of the pancreas are
located.
- Alpha cells secrete glucagon
raises blood sugar,
important between meals for increasing the supply of glucose.
- Beta cells secrete insulin
lowers blood sugar (after meals),
also promotes the conversion of glucose into glycogen, glycogen and proteins into muscle and
fats into adipose tissue.
- Delta cells secrete somatostatin
function not well understood, thought to inhibit the secretion of glucagon and insulin.
Recap
Hormones secreted by the pancreas include glucagon, insulin and somatostatin. Glucagon raises
blood glucose levels by increasing production of glucose from glycogen. Insulin lowers glucose levels
by facilitating glucose uptake and storage. Somatostatin inhibits the secretion of both glucagon and
insulin.
13.5 THE ADRENAL GLANDS COMPRISE THE CORTEX AND MEDULLA
Adrenal glands
= two small endocrine glands located just above the kidneys,
the cortex and medulla function as two separate endocrine glands.
The adrenal cortex: Glucocorticoids and mineralocorticoids
(Cortex produces small amounts of sex hormones, discussed later)
Two classes of steroid hormones:
- Glucocorticoids: Cortisol
During prolonged fasting:
assists in maintaining blood glucose levels by promoting the utilization of fats and by
increasing the breakdown of the protein to amino acids in muscle.
Secretion is controlled by a feedback loop.
- Mineralocorticoids: Aldosterone
Primarily responsible for regulating the amounts of sodium and potassium in the body,
so with ADH it helps maintain body water balance.
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The adrenal medulla: Epinephrine and norepinephrine
Nonsteroid hormones: epinephrine and norepinephrine,
which play roles in metabolism and controlling blood pressure and heart activity.
- Raise blood glucose levels, increase heart rate and force of contraction, increase
respiration rate, constrict or dilate blood vessels in many organs:
fight or flight responses
Adrenal medulla = neuroendocrine organ.
Recap
The main secretory products of the adrenal cortex are cortisol and aldosterone. Cortisol raises blood
glucose levels and suppresses inflammatory responses. Aldosterone regulates water balance by
promoting sodium reabsorption. The hormones secreted by the adrenal medulla contribute to the
fight-or-flight response initiated by the sympathetic nervous system.
13.6 THYROID AND PARATHYROID GLANDS
Thyroid gland
= situated just below the larynx at the front of the trachea.
Parathyroid glands
= embedded in the back of the thyroid.
anatomically and functionally linked.
The thyroid gland: Thyroxin speeds cellular metabolism
Thyroxine and triiodothyronine
structurally not a steroid hormone, but it acts like a steroid hormone because it is lipid soluble,
increases the production and use of ATP from glucose in nearly all body cells.
- Iodine deficiency can cause goiter
Production of active thyroid hormones requires iodine, iodine deficiency can result in a
thyroid-deficiency disease.
When thyroxine is absent or too low, the normal feedback inhibitory controls on the
hypothalamus and pituitary are missing, so they secrete large quantities of the releasing
hormone and TSH.
This causes the thyroid gland to grow to enormous size = goiter.
- Calcitonin promotes bone growth
Calcitonin
other main hormone of the thyroid gland, decreases the rate of bone resorption,
by inhibiting the activity of osteoclasts.
It is particularly important for the growth and development of the bones in children.
Parathyroid hormone controls blood calcium levels
Parathyroid hormone
removes calcium and phosphate from bone,
increases absorption of calcium by the digestive tract,
causes the kidneys to retain calcium and excrete phosphate.
together: raise the blood calcium level.
57

Recap
Production of the thyroid gland hormones requires iodine. T 3 and T 4 speed cellular metabolism and
have widespread effects on growth in children and basal metabolic rate in adults. Calcitonin lowers
blood calcium levels and PTH raises blood calcium.
13.7 TESTES AND OVARIES PRODUCE SEX HORMONES
Testes produce testosterone
- Testes produce androgens, the male sex hormones: testosterone.
- Before birth:
responsible for the development of the external male genitalia.
- Between birth and puberty: no testosterone production.
- Puberty:
LH stimulates the testes to resume testosterone production.
spurt of bone and muscle growth, secondary sex characteristics!
- Regulates the development and normal functioning of sperm, the male reproductive
organs and male sex drive.
Ovaries produce estrogen and progesterone
- Ovaries produce estrogens, the female sex hormones and progesterone.
- Puberty:
LH and FSH stimulate the ovaries to begin secreting estrogen and progesterone.
- Estrogen initiates the development of female secondary sex characteristics.
- Both estrogen and progesterone regulate the menstrual cycle.
13.8 OTHER GLANDS AND ORGANS ALSO SECRETE HORMONES
Thymus gland hormones aid the immune system
- Thymus gland
located between the lungs, behind the breastbone, near the heart.
- Thymosin and thymopoietin
help lymphocytes develop into mature T cells.
Endocrine functions of the hearth, the digestive system and the kidneys
- Atrial natriuretic hormone (ANH)
peptide (nonsteroid) hormone secreted by the atria of the heart,
helps regulate blood pressure.
- Gastrin, secretin and cholecystokinin
hormones secreted by the digestive system,
have effects on the stomach, pancreas and gallbladder.
- Erythropoietin and renin
hormones secreted by the kidneys,
erythropoietin stimulates the production of RBCs in the bone marrow,
renin (=an enzyme), critical component of the renin-angiotensin system (Ch. 15).
13.9 OTHER CHEMICAL MESSENGERS
58

13.10 DISORDERS OF THE ENDOCRINE SYSTEM
Diabetes mellitus: Inadequate control of blood sugar
Diabetes
= disease of sugar regulation, inability to get glucose into cells where it can be used.
- Dehydration and thirst, fatigue, frequent infections, blurred vision, cuts that are slow to
heal, tingling in the feet or hands.
- Type 1 diabetes
caused by the failure of the pancreas to produce enough insulin.
- Type 2 diabetes
caused by insulin resistance.
lifestyle factors have an important role!!
Hypothyroidism: Underactive thyroid gland
Hypothyroidism
= underactivity of the thyroid gland, hyposecretion of thyroid hormones.
- Variety of symptoms.
- In children: can slow body growth, alter brain development, delay the onset of puberty.
Can result in cretinism, a condition of mental retardation and stunted growth.
- In adults: can lead to myxedema:
edema under the skin, lethargy, weight gain, low BMR, low body temperature.
Hyperthyroidism: Overactive thyroid gland
Hyperthyroidism
= an overactive thyroid gland, hypersecretion of thyroid hormones.
- Increases BMR, causes hyperactivity, nervousness, agitation and weight loss.
- Graver’s disease:
autoimmune disorder, antibodies stimulate the thyroid to produce too much thyroxine.
Addison’s disease: Too little cortisol and aldosterone
Addison’s disease
= caused by failure of the adrenal cortex to secrete sufficient cortisol and aldosterone.
(lowers blood glucose levels, lowers blood sodium)
- Develops slowly:
fatigue, weakness, abdominal pain, weight loss, “bronzed” skin color.
Cushing’s syndrome: Too much cortisol
Cushing’s syndrome
= caused by too much cortisol,
excessive production of glucose from glycogen and protein,
retention of too much salt and water.
- Fatigue, edema, high blood pressure.
- Can be caused by rumors of the adrenal gland or the ACTH-secreting cells of the pituitary
or by excessive use or cortisol and cortisol-like drugs.
59

14 THE DIGESTIVE SYSTEM AND NUTRITION
14.1 THE DIGESTIVE SYSTEM BRINGS NUTRIENTS INTO THE BODY
Gastrointestinal tract.
Lumen = space within the hollow tube, through which food and liquids travel.
The walls of the GI tract are composed of four layers
- Mucosa
= mucous membrane in contact with the lumen;
- Submucosa
= layer of connective tissue containing blood vessels, lymph vessels and nerves;
- Muscularis
= two/three layers of smooth muscle, inner layer = circular, outer layer = lengthwise;
(stomach has a diagonal sublayer inside the other two)
- Serosa
= thin connective tissue sheath that surrounds and protects the other layers and attaches
the digestive system to the walls of the body cavity.
Five basic processes accomplish digestive system function
- Mechanical processing and movement;
- Secretion;
- Digestion;
- Absorption;
- Elimination.
Two types of motility aid digestive processes
- Peristalsis
= propels food forward (figure 14.3a)
- Segmentation
= mixes food (figure 14.3b)
Recap
The digestive system consists of organs and accessory organs that share the function of bringing
nutrients into the body. The wall of the GI tract consists of four tissue layers: mucosa, submucosa,
muscularis and serosa. The five basic processes of the digestion are mechanical processing and
movement, secretion, digestion absorption and elimination.
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14.2 THE MOUTH PROCESSES FOOD FOR SWALLOWING
Teeth bite and chew food (figure 14.4a and b)
The tongue positions and tastes food
Tongue = skeletal muscle enclosed in mucous membrane.
Saliva begins the process of digestion
- Salivary glands (three pairs) produce saliva
• Mucin
= mucus-like protein that holds food particles together, so they can be
swallowed more easily;
• Salivary amylase
= enzyme that begins the digestion of carbohydrates;
• Bicarbonate
= maintains the pH of the mouth, help protect teeth against bacteria;
• Lysozyme
= enzyme that inhibits bacterial growth.
Recap
The four kinds of teeth (molars, premolars, canines and incisors) mechanically digest chunks of food.
Salivary glands secrete saliva, which moistens food begins the chemical digestion of carbohydrates,
maintains the pH of the mouth and protects the teeth against bacteria.
14.3 THE PHARYNX AND ESOPHAGUS DELIVER FOOD TO THE STOMACH (FIGURE 14.6):
Swallowing
- Voluntary phase
movements of the tongue and jaws push a bolus of food into the pharynx.
- Involuntary phase (swallowing reflex)
• The presence of the food stimulates receptors in the pharynx and initiates the
swallowing reflex;
• The soft palate rises to close off the passageway into the nasal cavity and the
larynx rises slightly.
• The epiglottis bends to close airway;
Meanwhile the tongue pushes the food back, sliding it past the epiglottis and
into the esophagus.
Esophagus
= muscular tube consisting of both skeletal and smooth muscle that connects the pharynx to the
stomach.
Acid reflux
= backflow of acidic stomach fluid into the esophagus, because of malfunction of the sphincter.
Hiatal hernia
= a condition in which part of the stomach protrudes upward into the chest through an opening
in the diaphragm muscle.
Recap
Swallowing begins with voluntary movements of the tongue; the presence of food initiates an
involuntary swallowing reflex. Peristalsis and gravity transfer food through the esophagus to the
stomach.
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14.4 THE STOMACH STORES FOOD, DIGESTS PROTEIN AND REGULATES DELIVERY
Stomach
= muscular, expandable sac:
• Food storage;
• Digestion;
• Regulation of delivery.
Gastric juice breaks down proteins
- Hydrochloric acid (HCl), mucus, pepsinogen (becomes pepsin once in the stomach),
intrinsic factor (protein), gastrin (hormone).
- Pepsin
= protein-digesting enzyme;
- Chime
= watery mixture of partially digested food and gastric juice, delivered to the intestine.
- Peptic ulcer
= if the mucous layer becomes damaged, this leaves the underlying tissue vulnerable, an
open sore may form.
Stomach contractions mix food and push it forward
peristaltic movement
Recap
The stomach stores food, digests it and regulates its delivery to the small intestine. Gastric juice
dissolves connective tissue, large proteins and peptides in food. The presence of food stretches the
stomach and increases peristalsis. Peristaltic contractions mix the chime and push it gradually into
the small intestine.
14.5 THE SMALL INTESTINE DIGESTS FOOD AND ABSORBS NUTRIENTS AND WATER
Digestion
- Protein digestion continues, also digestion of carbohydrates and lipids;
- Involves neutralizing the highly acidic gastric juice and adding additional digestive
enzymes (from the intestine and pancreas).
Absorption
- Single amino acids, monosaccharides, fatty acids and glycerol are absorbed.
Three regions:
- Duodenum
- Jejunum
- Ileum
Structure of the intestine wall
Villi with epithelial cells each epithelial cell has smaller microvilli.
Recap
The small intestine has two major functions: digesting proteins, carbohydrates and lipids and
absorbing 90% of the nutrients and water we consume. Projections called villi in the mucosa increase
the small intestine’s surface area for absorption.
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14.6 ACCESSORY ORGANS AID DIGESTION AND ABSORPTION
The pancreas secretes enzymes and NaHCO 3
- Secretes:
• Digestive enzymes
(including proteases; pancreatic amylase; lipase);
• Sodium bicarbonate (NAHCO 3 )
to neutralize stomach acid.
- Two pancreatic ducts deliver these secretions to the duodenum.
The liver produces bile and performs many other functions
- Produces bile
= a watery mixture containing electrolytes, cholesterol, bile salts, lecithin (phospholipid)
and pigments (bilirubin).
- Hepatic portal system
= carries blood from one capillary bed to another: carries nutrient-rich blood from the
digestive organs to the liver via the hepatic portal vein.
- Other functions:
• Stores fat-soluble vitamins (A,D,E,K);
• Stores glucose as glycogen and converts glycogen back to glucose;
• Manufactures plasma proteins from amino acids;
• Synthesizes and stores some lipids;
• Inactivates many chemicals (alcohol, hormones, drugs, poisons…);
• Converts ammonia (NH 3 ) into urea;
• Destroys worn-out RBCs.
The gallbladder stores bile until needed
- Gallbladder,
bile is secreted into the small intestine via the bile duct, which joins the pancreatic duct.
Recap
The pancreas secretes digestive enzymes and sodium bicarbonate. The sodium bicarbonate
neutralizes stomach acid, making the digestive enzymes more effective. The liver produces bile,
which is stored in the gallbladder until after a meal. The liver also produces plasma proteins; inactive
toxic chemicals; destroys old RBCs; stores vitamins, iron and certain products of metabolism and
performs other functions important for homeostasis.
14.7 THE LARGE INTESTINE ABSORBS NUTRIENTS AND ELIMINATES WASTES
Figure 14.12!
Recap
The large intestine absorbs the last of the water, ions and some nutrients and stores fees until
defecation occurs.
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14.8 HOW NUTRIENTS ARE ABSORBED
Proteins and carbohydrates are absorbed by active transport
Lipids are broken down, then reassembled
Water is absorbed by osmosis
Vitamins and minerals follow a variety of paths
Recap
Proteins and carbohydrates are transported into the cells lining the small intestine by active
transport processes, then diffuse into capillaries. The products of lipid digestion are transported to
the mucosa in micelles, diffuse into the cell and recombine into lipids within the cell. Then they are
coated with protein to become chylomicrons that enter the lymph. The intestines also absorb water,
vitamins, minerals and digestive secretions
14.9 ENDOCRINE AND NERVOUS SYSTEM REGULATE DIGESTION
Regulation depends on volume and content of food
- Gastrin (in the stomach)
= hormone, released when the stomach is stretched and when protein is present,
triggers the release of more gastric juice.
- Secretin (duodenum)
= hormone, acid in chime triggers release,
stimulates the pancreas to secrete water and bicarbonate (to neutralize the acid).
- Cholecystokinin (CCK) (duodenum)
= hormone, fat and protein stimulate release,
signals the pancreas to secrete more digestive enzymes.
- Stretching of the duodenum + CCK gallbladder releases bile
Nutrients are used or stored until needed
Three basic concepts:
- Lipids, carbohydrates and proteins can all be converted to storage forms of lipid or
carbohydrate, then be recycled according to the body’s needs.
- When we consume more nutrients than we use, our bodies store the excess for future
use.
- When we consume fewer energy-containing nutrients than we use, the body draws on
these storage forms of energy.
Recap
The endocrine and nervous systems regulate digestion based on content and volume of food.
Regulatory mechanisms include neural reflexes involving organ stretching and release of the
hormones gastrin, secretin and cholecystokinin. Amino acids and the products of lipid and
carbohydrate digestion can all be converted to storage forms of lipid or carbohydrate, to be retrieved
and used when needed.
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14.10 NUTRITION: YOU ARE WHAT YOU EAT
Carbohydrates: A major energy source
Lipids: Essential cell components and energy source
- Saturated fats vs. unsaturated fats.
Complete proteins contain every amino acid
- Essential amino acids (the body cannot produce, must come from food)
- Complete protein (contains all 20 amino acids)
Vitamins are essential for normal function
- Vitamin D
promotes absorption of calcium, required for healthy bones and teeth;
--- : bone deformities in children, bone weakening in adults,
+++: calcium deposits in tissues (leading to cardiovascular and kidney damage).
- Vitamin B 1
coenzyme in carbohydrate metabolism;
--- : damage to heart and nerves, pain.
- Vitamin B 12
coenzyme in nucleic acid metabolism;
--- : anemia, nervous system damage.
- Vitamin C
antioxidant; needed for collagen formation; important for bone and teeth formation;
improves iron absorption;
--- : scurvy, poor wound healing, impaired immune responses,
+++: digestive upsets.
Minerals: Elements essential for body processes
- Recommended dietary allowance.
Fiber benefits the colon
- Hemorrhoids
= swollen veins in the lining of the anus, caused by a low-fiber diet.
- Diverticulosis
Recap
A healthy diet includes plenty of fruits, vegetables and whole grains and adequate fiber. Saturated
fat, sugar, salt and alcohol should be ingested only in modest amounts. Some essential fatty acid and
eight essential amino acids must be ingested to meet the body’s nutritional requirements because
the body cannot synthesize them. Complete proteins contain all 20 amino acids. Most animal
proteins are complete, but most plant proteins are incomplete. All minerals and nearly all vitamins
must be obtained from food.
65

14.11 WEIGHT CONTROL: ENERGY CONSUMED VERSUS ENERGY SPENT
BMR: Determining how many calories we need
- BMR = the energy the body needs to perform essential activities and maintaining organ
function, influenced by the following factors:
• Gender and body composition;
• Age;
• Health;
• Stress;
• Food intake;
• Genetics.
Energy balance and body weight
Physical activity: An efficient way to use calories
Healthy weight improves overall health
- BMI (body mass index)
Recap
Weight control involves balancing energy consumed in food against energy spent. Calculating your
BMR helps you estimate how many calories you need each day. Increasing physical activity is an
efficient way to increase calorie expenditure. The best strategy for losing weight combines a healthy
diet with moderate regular exercise.
14.12 DISORDERS OF THE DIGESTIVE SYSTEM
Disorders of de GI tract
- Food poisoning and food allergies.
- Lactose intolerance: Difficulty ingesting milk
Adults lose the enzyme lactase over time and so their ability to digest lactose.
- Peptic ulcers: sores in the stomach
= erosions of the mucosal lining of the stomach or duodenum,
mostly associated with infection by Helicobacter pylori.
- Celiac disease (gluten intolerance)
= immune system responds by damaging or destroying the villi that line the small
intestine, when gluten are ingested.
- Diverticulosis: Weakness in the wall of the large intestine
• Diverticulitis = inflammation of the diverticula.
- Colon polyps: Noncancerous growths
= a noncancerous growth that projects from a mucous membrane.
• Colonoscopy (detect and remove polyps)
66

Disorders of the accessory organs
- Hepatitis: Inflammation of the liver
= generally caused by viruses or toxic substances.
• Hep A
transmitted by contaminated food or water, brief illness, vaccine;
• Hep B
usually transmitted via contaminated needles, blood transfusion, sexual contact,
can lead to liver failure, vaccine;
• Hep C
transmitted via contaminated needles or blood transfusion,
remains silent, but can damage the liver severely,
(can lead to chronic hepatitis, cirrhosis, liver cancer).
- Gallstones can obstruct bile flow
Malnutrition: Too many or too few nutrients
= conditions in which human development and function are compromised by an unbalanced or
insufficient diet:
- Overnutrition
obesity
- Undernutrition
e.g. vitamin A deficiency eye damage and night blindness
Recap
Disorders of the GI tract and accessory organs include lactose intolerance, diverticulosis, colon
polyps, gallstones and hepatitis. Malnutrition can be caused by under-or overnutrition. Whereas
starvation is the leading cause of malnutrition in underdeveloped countries, obesity is increasing in
industrialized countries.
14.13 EATING DISORDER: ANOREXIA NERVOSA AND BULIMIA
Eating disorders
- Anorexia nervosa
= condition in which a person diets excessively or stops eating, even to the point of
starvation and death.
- Bulimia
= binge-and-purge condition in which someone eats and deliberately vomits or takes
other steps to minimize the calories ingested.
67

15 THE URINARY SYSTEM
15.1 THE URINARY SYSTEM CONTRIBUTES TO HOMEOSTASIS
Excretion = processes that remove wastes and excess materials from the body.
Urinary system = kidneys, ureters, bladder, urethra.
The kidneys regulate water levels
Water input equals water output homeostasis
The kidneys regulate nitrogenous wastes and other solutes
Metabolism of proteins liberates ammonia (NH 3 ), which is toxic to cells.
The liver detoxifies it by combining two ammonia molecules with a molecule of carbon dioxide,
producing urea and water. Most of the urea is excreted by the urinary system.
Recap
The urinary system maintains a constant internal environment by regulation water balance and body
levels of nitrogenous wastes, ions and other substances. It filters metabolic wastes from the blood
and excretes them in urine. The major nitrogenous waste product is urea.
15.2 ORGANS OF THE URINARY SYSTEM
figure 15.2!
Kidneys: The principal urinary organs
- Each kidney consist of inner pyramid-shaped zones of dense tissue (renal pyramids) that
constitute the medulla,
- And an outer zone, the cortex.
- At the center of the kidney is a hollow space, the renal pelvis.
- Kidney function besides excretion:
• Control RBC production (produce erythropoietin);
• Activate vitamin D.
Ureters transport urine to the bladder
Ureter = muscular tube that transports urine from the kidneys to the bladder.
Urinary bladder stores urine
Bladder = stores urine, consist of 3 layers of smooth muscle, line on the inside by epithelial cells.
Urethra carries urine from the body
Urethra = carries urine from the bladder to the body’s external opening,
internal urethral sphincter (between bladder and urethra)
and external urethral sphincter (end of urethra) prevent the bladder from emptying.
Recap
Organs of the urinary system include the kidneys, ureters, bladder and urethra. The kidneys are the
principal urinary organs, although they have several homeostatic functions as well. The ureters
transport urine into the bladder, where it is stored until carried by the urethra to the body’s exteral
opening.
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15.3 NEPHRONS PRODUCE URINE
Nephrons = small functional units,
consists of a hollow tube of epithelial cells (tubule) and the blood vessels that supply the tubule.
produce urine.
The tubule filters fluid and reabsorbs substances
- Glomerular capsule (Bowman’s capsule)
surrounds and encloses a network of capillaries, the glomerulus, which is part of the
blood supply to the nephron.
- Tubule
continues as a long, thin tube:
• The proximal tubule (glomerular capsule to medulla);
• Loop of henle (into the medulla (descending limb),
and back up to the glomerular capsule (ascending limb));
• The distal tubule (after it passes the glomerular capsule);
• Collecting duct (from the cortex to the renal pelvis).
Special blood vessels supply the tubule
- Afferent arteriole
every nephron is supplied by a single arteriole.
- Efferent arteriole
= the glomerular capillaries rejoin to become the efferent arteriole,
carries filtered blood from the glomerulus.
divides again into another capillary network:
- Peritubular capillaries
= surrounds the proximal and distal tubules in the cortex,
remove water, ions and nutrients.
- Vasa recta
the efferent arterioles of a few nephrons descend into the medulla and divide into long,
thin capillaries called vasa recta,
supply the loop of Henle and collecting duct.
Recap
A nephron is the functional unit of a kidney. A nephron tubule consist of a glomerular capsule, where
fluid is filtered and four regions in which the filtrate is modified before it becomes urine: proximal
tube, loop of Henle, distal tubule and collecting duct. Blood flows to the glomerulus via the renal
artery and afferent arterioles. Peritubular capillaries carry the blood to the proximal and distal
tubules and vasa recta supply the loops of Henle and collecting ducts.
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15.4 FORMATION OF URINE: FILTRATION, REABSORPTION AND SECRETION
1. Glomerular filtration
= movement of a protein-free solution of fluid and solute from the glomerulus into the space within
the glomerular capsule;
2. Tubular reabsorption
= return of most of the fluid and solutes back into the peritubular capillaries or vasa recta;
3. Tubular secretion
= addition of certain solutes from the peritubular capillaries or vasa recta into the tubule.
Glomerular filtration filters fluid from capillaries
- Filtration barrier:
• Podocytes
= modified tubular epithelial cells that cover and surround the outside surface of
the capillaries;
• The capillary cells.
- Podocytes = less permeable to large proteins and whole cells
filtered fluid contains water and small solutes, in the same concentration found in
blood plasma, but no large proteins or blood cells.
- Rate of filtration is regulated in two ways:
• Resting conditions
pressure-sensitive cells in the arterioles and flow-sensitive cells in the tubule
walls can release chemicals to adjust the diameter of the afferent arterioles
relatively constant rate of glomerular filtration;
• Times of stress
blood flow to the kidneys falls (blood is redistributed to more critical organs),
the sympathetic nervous system constricts afferent and efferent arterioles,
reducing blood flow and the rates of glomerular filtration and urine formation.
- Proteinuria =appearance of protein in urine, a sign of glomerular damage.
Tubular reabsorption returns filtered water and solutes to blood
= returns filtered water and solutes into the blood of the peritubular capillaries or vasa recta.
- Active transport of sodium out of the proximal tubular cell decreases intracellular
concentration of sodium
sodium enters the cell by facilitated transport;
- Sodium = + charged
its movement drives the diffusion of chloride across the tubular cell
(Chloride = - charged: follows to maintain balance)
- Transport of solutes (Na + and Cl - ) creates a concentration gradient for the diffusion of
water
water is reabsorbed, through special water channels in membrane proteins
(aquaporins)
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Tubular secretion removes other substances from blood
Either by active transport or passive diffusion, some substances move from the capillaries into
the tubule
critical for removing or regulating levels of certain chemicals.
Hydrogen (H + ), ammonium (NH 4 - ) secreted to maintain acid-base balance,
potassium (K + ) also secreted.
Recap
In the glomerulus, glomerular filtration separates some of the plasma fluid and small solutes from
larger proteins and blood cells. Tubular reabsorption returns nearly all the filtered water and sodium
and all the major nutrients back to the peritubular capillaries or vasa recta. Tubular secretion
removes toxic, foreign and excess substances from the peritubular capillaries or vasa recta. Tubular
secretion is essential to the regulation of acid-base balance, potassium balance and the excretion of
certain wastes.
15.5 THE KIDNEYS CAN PRODUCE DILUTE OR CONCENTRATED URINE
Producing dilute urine: Excreting excess water
reabsorb less water.
Producing concentrated urine: Conserving water
The process of reabsorbing water is regulated by antidiuretic hormone.
increases the permeability of the collecting duct to water,
so more water is reabsorbed because it diffuses out of the collecting duct toward the higher
solute concentration in the medulla.
Recap
Production of dilute urine requires the reabsorption of salt without the concurrent reabsorption of
water in the ascending limb of the loop of Henle, the distal tubule and the collecting duct. The
formation of concentrated urine requires antidiuretic hormone. In the presence of ADH, most of the
water is reabsorbed from the collecting duct leaving a small volume of concentrated urin to be
excreted.
15.6 URINATION DEPENDS ON A REFLEX
Micturition reflex:
sensory nerves are stimulated by stretching of the bladder, send signal to the spinal cord
an involuntary reflex contracts the smooth muscle of the bladder and relaxes the internal urethral
sphincter.
Voluntary control of the external urethral sphincter!
Recap
Urination depends on the neural micturition reflex; bladder stretching initiates involuntary relaxation
of the internal urethral sphincter. The brain can override the reflex by voluntary contraction of the
external urethral sphincter.
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15.7 THE KIDNEYS MAINTAIN HOMEOSTASIS IN MANY WAYS
ADH regulates water balance
(see 15.5)
Diuresis = high urine flow rate,
diuretic = any substance that increases the formation and excretion of urine (e.g. caffeine)
Aldosterone regulates salt balance
Aldosterone
= steroid hormone from the adrenal gland, regulates sodium excretion.
High aldosterone concentration = nearly all the filtered sodium is reabsorbed.
controlled by the renin-angiotensin system.
The renin-angiotensin system controls bloods volume and blood pressure
- Angiotensin 2 = peptide that functions like a hormone.
- Renin = enzyme,
synthesized and stored in specialized cells of the afferent arteriole in region near the
glomerulus, the juxtaglomerular apparatus;
- P. 370 + figure next page
Atrial natriuretic hormone protects against blood volume excess
ANH (peptide hormone) inhibits sodium reabsorption in the distal tubules and collecting ducts,
which leads to increased sodium excretion
ADH causes water to follow salt in order to keep the blood solute concentration constant.
(Opposite of aldosterone:
ANH: protects against salt and water excess, aldosterone: protects against salt and water deficit).
Kidneys help maintain acid-base balance and blood pH
- Reabsorption of filtered bicarbonate;
- Excretion of acid as ammonium.
Erythropoietin stimulates production of RBCs
Kidneys secrete erythropoietin stimulates red bone marrow to produce more RBCs.
Kidneys activate vitamin D
An inactive form of vitamin D, altered by the liver, is converted to its active from in the kidneys
under the influence of parathyroid hormone (PTH), from the parathyroid glad.
Recap
ADH controls blood total solute concentration, aldosterone controls blood sodium concentration and
the combination of renin-angiotensin, aldosterone and ANF controls blood volume. The kidneys help
maintain the body’s acid-base balance and blood pH by reabsorbing all filtered bicarbonate and by
excreting H + . Decreased oxygen delivery to the kidneys triggers the release of erythropoietin, which
stimulates the production of RBC by bone marrow. The kidneys activate an inactive form of vitamin D
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15.8 DISORDERS OF THE URINARY SYSTEM
Kidney stones can block urine flow
Kidney stones = crystallized minerals in the renal pelvis that form solid masses,
can cause great pain when obstructing a ureter.
Urinary tract infections are often caused by bacteria
Urinary tract infection = the presence of microbes in urine or an infection in any part of the
urinary system,
caused by bacteria.
Acute and chronic renal failure impair kidney function
= damage to the kidneys, reducing function.
- Acute renal failure: short term and possibly correctable,
caused by very low blood pressure, large kidney stones, infections, transfusion reactions,
burns, severe injuries, toxic drugs or chemicals.
- Chronic renal failure: long-term, irreversible damage.
Dialysis cleanses the blood artificially
Dialysis attempts to duplicate the functions of healthy kidneys:
- Continuous ambulatory peritoneal dialysis (CAPD):
dialysis fluid is placed into the peritoneal cavity, where it exchanges wastes and ions with
the capillaries. Then the fluid is drained and discarded.
- Hemodialysis:
patient’s blood is circulated through an artificial kidney machine.
Kidney transplants are a permanent solution to renal failure
Recap
Acute or chronic renal failure can result from prolonged changes in blood pressure, disease, large
kidney stones, transfusion reactions, burns, injuries, toxic substances and other conditions such as
diabetes. When kidneys fail, dialysis may be needed to keep the patient alive. Kidney transplants are
the best hope for people in renal failure.
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16 REPRODUCTIVE SYSTEMS
16.1 THE MALE REPRODUCTIVE SYSTEM DELIVERS SPERM
Testes produce sperm (P. 379 fig. 16.1)
- Testes
= sites of sperm production, descend into the scrotum shortly before birth.
- Sperm =male reproductive cells, stored in the epididymis and ductus deferens.
- Seminiferous tubules, located in the testes,
where the sperm are produced, join to become the epididymis.
- Epididymis
= a single coiled duct outside the testis, joins the ductus deferens.
- Ductus (vas) deferens
joins the duct coming from the seminal vesicle, to become the ejaculatory duct.
- Penis
= male organ of sexual intercourse, delivers sperm into the female, contains erectile
tissues that permit erection, an increase in length, diameter and stiffness.
Accessory glands help sperm survive
- Semen
thick, whitish mixture of fluids, contains sperm, secretions from the seminal vesicles,
prostate gland and bulbourethral gland.
- Seminal vesicles (zaadblaasjes)
produce seminal fluid, a watery mixture (about 60% of the semen) containing
• Fructose
provides the sperm with a source of energy;
• Prostaglandins
induce muscle contractions in the female reproductive system that help sperm
travel more effectively.
- Prostate gland
contributes an alkaline fluid, to raise the vaginal pH to about 6, optimal for sperm.
- Bulbourethral gland(Cowper’s gland)
secrete mucus into the urethra during sexual arousal, it washes away traces of acidic
urine before the sperm arrive.
- The sperm are not mixed with the fluids until the moment of ejaculation.
Sperm production requires several cell divisions (P. 381 fig. 16.2!! (especially b and d))
- Spermatogonia = undifferentiated, diploid cells.
- Gametes = haploid cells, formed by mitosis and meisosis. (Ch. 17)
- Sertoli cells
= large cells in the seminiferous tubules that surround and nourish the spermatids.
- A sperm:
• Tail, produces whiplive movements which propel the sperm;
• Midpiece, containing mitochondria that produce energy for the sperm;
• Head, contains the male’s chromosomes;
• Acrosome, contains enzymes that help the sperm penetrate the egg.
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Testosterone affects male reproductive capacity
- P. 382 fig.16.3
- Testosterone
= steroid hormone produces by interstitial cells (located between the seminiferous
tubules within the testes),
controls the growth and function of the male reproductive tissues,
stimulates aggressive and sexual behavior,
causes the development of secondary sexual characteristics.
Within the testes, testosterone stimulates the undifferentiated spermatogonia to begin
dividing and the Sertoli cells to support the developing sperm.
- Gonadotropin-releasing hormone (GnRH)
from the hypothalamus, stimulates the release of LH and FSH.
- Luteinizing hormone (LH)
Follicle-stimulating hormone (FSH)
from the anterior pituitary gland, stimulate the reproductive organs.
- Inhibin
from the Sertoli cells when highly active, directly inhibits the secretion of FSH.
- Feedback control loop:
• Contains blood testosterone concentration and sperm production relatively
constant over time;
• The hypothalamus secretes GnRH, which stimulates the release of LH and FSH,
when blood levels of testosterone fall.
LH stimulates the secretion of testosterone by the interstitial cells,
FSH seems to enhance sperm formation by stimulating the Sertoli cells.
• Excessively high testosterone concentrations inhibit GnRH, LH and FSH secretion.
• Highly active Sertoli cells, secrete inhibin, which inhibits FSH secretion.
Recap
The male reproductive system comprises the testes, the penis and associated ducts and glands.
Semen consists of sperm and three glandular secretions that provide energy and the proper pH
environment for the sperm and also lubrication for sexual intercourse. Millions of sperm form every
day throughout a man’s life; a typical ejaculate contains up to 300 million. Testosterone stimulates
the growth and function of the male reproductive system and encourages aggressive and sexual
behavior. Blood levels of testosterone are regulated by a negative feedback loop involving GnRH
from the hypothalamus and LH and FSH from the anterior pituitary.
16.2 THE FEMALE REPRODUCTIVE SYSTEM PRODUCES EGGS AND SUPPORTS PREGNANCY
Ovaries release oocytes and secrete hormones
- P. 383 fig. 16.4!!
- Ovaries
= primary female reproductive organs, release the female gametes, oocytes,
also secret estrogen and progesterone, the female sex steroid hormones.
- Oviduct
= or Fallopian tube, leads from the ovary to the uterus.
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The uterus nurtures the developing embryo
- Uterus
= hollow, pear-shaped organ where the embryo grows and develops.
- Endometrium = inner layer of the uterus,
lining of epithelial tissue, glands, connective tissue and blood vessels.
(Implantation, an egg attaches to the endometrium; helps forming the placenta).
- Myometrium = outer layer of the uterus,
thick layers of smooth muscle, stretches during pregnancy, provides the force to expel
the fetus during labor.
- Cervix = narrow lower part of the uterus.
The vagina: Organ of sexual intercourse and birth canal
- Vagina
= hollow muscular organ of sexual intercourse and also the birth canal,
may be partially covered by the hymen..
- Vulva, all female external genitalia:
• Labia majora
larger pair of fat-padded skin folds,
labia minora
smaller, highly vascular pair of folds.
• Clitoris
small organ partly enclosed by the labia minora, contains erectile tissue.
Mammary glands nourish the infant
- Mammary glands
= modified sweat glands that are part of the skin,
specialized to produce milk (p. 384 fig. 16.5!).
- Nipples, surrounded by the pigmented areola.
- Lactation
the production of milk, stimulated by prolactin and oxytocin.
(The glands are prepared by estrogen and progesterone!)
Recap
The ovaries secrete estrogen and progesterone, store immature oocytes and release one oocyte at
intervals of about 28 days. The oocyte travels through the oviduct to the uterus, where implantation
occurs if the egg has been fertilized. The vagina is the female organ of sexual intercourse and the
birth canal; around its opening are the structures of the vulva. Mammary glands are accessory organs
that produce and store milk.
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16.3 MENSTRUAL CYCLE CONSIST OF OVARIAN AND UTERINE CYCLES
The ovarian cycle: Oocytes mature and are released
- Ovarian cycle
= regular pattern of growth, maturation and release of oocytes from the ovary.
- P. 385 fig. 16.6!
• Follicle
= primary oocyte + granulosa cells (that nourish it).
• Zona pellucida
= noncellular coating around the oocyte.
• Antrum
= fluid-filled space, develops within the follicle.
• Seconary oocyte + polar body
are formed when the first stage of meiosis is completed.
• Ovulation
follicle wall ruptures, releasing the secondary oocyte,
with its polar body, zona pellucida and surrounding granulosa cels.
When sperm makes contact with the oocyte and penetrates its outer membrane,
the oocyte completes meiosis to produce a mature egg or ovum.
• Corpus luteum
forms from what is left of the ruptured follicle,
secretes large amounts of progesterone and estrogen.
(If fertilization does not occur, it degenerates in 12 days.)
(If fertilization does occur, the chorion (a layer of tissue derived from the
embryo) starts to secrete human chorionic gonadotropin (hCG) which causes the
corpus luteum to produce progesterone and estrogen for another 10 weeks,
then the placenta takes over.)
- 1. Immature follicle;
2. Zona pellucida develops around the primary oocyte;
3. Fluid-filled antrum develops;
4. Follicle matures;
5. Ovulation, the follicle ruptures releasing the secondary oocyte;
6. Corpus luteum forms from ruptured follicle;
7a. Corpus luteum degenerates if pregnancy does not occur,
7b. Corpus luteum is kept active by hCG for another 10 weeks.
The uterine cycle prepares the uterus for pregnancy
- Uterine cycle
= a series of structural and functional changes that occur in the endometrium of the
uterus.
• 1-5: Menstrual phase
Menstruation = the process by which the endometrial lining disintegrates and its
small blood vessels rupture. The shed tissue and blood are excreted.
• 6-14: Proliferative phase
Rising levels of estrogen trigger the endometrial lining to proliferate, it becomes
thicker, more vascular and more glandular.
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• Ovulation
• 15-28: Secretory phase
Production of estrogen and especially progesterone (by the corpus luteum)
causes the endometrium to continue proliferating.
Uterine glands mature and produce glycogen as potential energy for the embryo.
The cervical mucus becomes thick and viscous, forming a “cervical plug”.
- Premenstrual syndrome (PMS)
= group of symptoms often associated with the premenstrual period;
food cravings, mood swings, anxiety, back and joint pain, water retention and headaches.
- Dysmenorrhea
= painful menstruation,
the endometrium of the uterus produces prostaglandins, which can trigger contractions
and cramping of the uterine smooth muscle.
Cyclic changes in hormone levels produce the menstrual cycle
(Read in book, p. 388)
- During the first half of the cycle LH and FSH stimulate follicular growth and development.
- The growing follicle secretes estrogen, which partially inhibits LH secretion.
- Shortly before the midpoint of the cycle, estrogen triggers the LH surge, which in turn
triggers ovulation.
- In the second half of the cycle, estrogen and progesterone from the corpus luteum
inhibit LH and FSH secretion, preventing maturation of another follicle, until it is
determined that pregnancy has not occurred.
Recap
During the ovarian cycle, a primary oocyte within a developing follicle divides once to form a
secondary oocyte. The follicle ruptures releases the oocyte and forms the corpus luteum that
secretes progesterone and estrogen. Rising levels of estrogen cause the endometrium to proliferate.
If pregnancy does not occur, hormone levels fall and the endometrial layer disintegrates and is shed.
Ovulation is triggered by a surge of LH, which in turn is caused by the positive feedback effect of a
high concentration of estrogen from the maturing follicle. During the second half of the menstrual
cycle, sustained high levels of estrogen and progesterone from the corpus luteum inhibit further
ovulation.
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16.4 HUMAN SEXUAL RESPONSE, INTERCOURSE AND FERTILIZATION
1. Excitement, increased sexual awareness and arousal;
2. Plateau, intense and continuing arousal;
3. Orgasm, the peak of sexual sensations;
4. Resolution, the abatement of arousal.
The male sexual response
- Erection occurs, when neural activity relaxes arterioles leading into vascular
compartments within the penis, the compartments fill with blood.
- Orgasm accomplishes ejaculation the expulsion of semen.
- During the resolution phase, the erection subsides and breathing and heart rate return
normal.
- A refractory period follows, during which another erection an orgasm cannot be
achieved, may last up to several hours.
The female sexual response
- Neural reflexes dilate blood vessels in the labia, clitoris and nipples.
- During arousal the vagina and area around the labia secrete lubricating fluids.
Fertilization: One sperm penetrates the egg
(see chapter 21)
Recap
Women and men experience the same four phases of sexual responsiveness. Sexual arousal in the
male results in penile erection that leads to orgasm and ejaculation. Females experience sexual
arousal and pleasurable orgasms marked by rhythmic muscular contractions. During ejaculation, the
male deposits several hundred million sperm in the vagina. Fertilization of the egg by a single sperm
occurs within 5 days, if it occurs at all.
16.5 BIRTH CONTROL METHODS: CONTROLLING FERTILITY
Abstinence: Not having intercourse
= only completely effective method of birth control.
Surgical sterilization: Vasectomy and tubal ligation
- Vasectomy = in males, tubal ligation = in females.
Hormonal methods: Pills, injections, patches and rings
- Birth control pills: synthetic progesterone and estrogen inhibits the release of FSH and
LH, so follicles do not mature and ovulation does not take place.
- Hormone injections, patches or rings = don’t have to be taken every day.
Provide reasonably effective and safe methods of birth control.
IUDs are inserted into the uterus
- Intrauterine devices, small plastic or metal pieces inserted into the uterus,
create a mild chronic inflammation that prevents fertilization or implantation.
Diaphragms and cervical caps block the cervix
- Diaphragms and cervical caps, latex devices inserted into the vagina,
covers the cervical opening, thus preventing sperm from entering the uterus.
Chemical spermicides kill sperm
Condoms trap ejaculated sperm
- Only one that prevents from STDs!
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Withdrawal and periodic abstinence
- Withdrawal, withdrawing the penis from the vagina right before ejaculation.
- Periodic abstinence, relying on the fact that fertilization is only possible for a limited time
in each cycle.
Both not very effective.
Pills that can be used after intercourse
- Morning-afterpills
contain high doses of progesterone and estrogen, or block the action of progesterone.
Elective abortion
- Elective termination of a pregnancy.
• Vacuum suctioning of the uterus;
• Surgical scraping of the uterine lining;
• Infusion of a strong saline solution that causes the fetus to be rejected.
The future in birth control
Diverse methods are being researched.
Recap
Surgical sterilization should be considered a permanent method of birth control. Hormonal methods
are also relatively effective. Physical barriers and chemical spermicides are moderately effective; a
few afford some protection against disease. IUDs are fairly effective against pregnancy but do not
protect against disease. Withdrawal and periodic abstinence are not effective forms of birth control
in the long term. Abortion is an elective but controversial procedure that terminates a pregnancy.
16.6 INFERTILITY: INABILITY TO CONCEIVE
Infertility can have many causes
- Male infertility = an insufficiency or lack of sperm.
- Female infertility can be caused by variable circumstances:
• Pelvic inflammatory disease
bacteria that migrate from the vagina to the oviducts can inflame the oviducts,
leading to scarring and partial or complete closure of the oviduct.
• Failure to ovulate, damage to oviducts, secretions that impair sperm function,
uterine tumors, age-related changes…
Enhancing fertility
- Artificial insemination
sperm are placed with a syringe into the vagina or uterus.
- Artificial reproductive technologies
In vitro fertilization (IVF)
the eggs mature in laboratory glassware under sterile conditions,
then sperm are added and when cells are dividing, the embryo is placed into the
woman’s uterus.
• Gamete intrafallopian transfer (GIFT)
unfertilized eggs and sperm are placed into an oviduct, without waiting for the
embryo to develop;
• Zygote intrafalopian transfer (ZIFT)
the fertilized egg is placed into the oviduct.
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- Fertility-enhancing drugs
medication to boost the production of developing eggs, sometimes tried before IVF or
given to women who are preparing for IVF.
- Surrogate motherhood
another woman becomes pregnant and bears the baby.
Recap
Male infertility is an insufficiency or lack of sperm. Causes of female infertility are variable and
include failure to ovulate, damage to oviducts, pelvic inflammatory disease, secretions that impair
sperm function, uterine tumors, endometriosis, age-related changes and miscarriages. The choice of
options to improve fertility depends on the case of the infertility. Options include artificial
insemination, in vitro fertilization, gamete intrafallopian transfer, zygote intrafallopian transfer,
fertility-enhancing drugs and surrogate motherhood.
16.7 SEXUALLY TRANSMITTED DISEASES
Bacterial STDs: Gonorrhea, syphilis and chlamydia
- Gonorrhea
- Syphilis
if not treated, both can cause inflammation and sterility.
- Chlamydia
can cause damage to body systems and eventually death.
Viral STDs: HIV, hepatitis B, genital herpes and HPV
- Hepatitis B and HPV can be prevented by a vaccine.
- HIV, discussed in Ch. 9.
Other STDs: Yeast infections, trichomoniasis and pubic lice
Protecting yourself against STDs
- Choose your partner wisely;
- Communicate with your partner;
- Use a barrier method of birth control.
Recap
Major bacterial STDs include gonorrhea, syphilis and chlamydia. The most dangerous viral STD is HIV.
Hepatitis B can be prevented by a vaccine. Genital herpes is irritating but not particularly deadly. HPV
can cause warts and is a risk factor for cervical cancer, it can be prevented by a vaccine. Yeast,
normally present in the vagina, can multiply and cause a yeast infection. Pubic lice are tiny
arthropods that are transmitted during intimate contact or by contact with clothes or bedding. You
can reduce your risk of contracting an STD with a little effort. Choose your partner wisely, use a
barrier method and if you suspect you have a disease, get tested promptly.
81

17 CELL REPRODUCTION AND DIFFERENTIATION
17.1 THE CELL CYCLE CREATES NEW CELLS
Cell cycle = repetitive sequence of events, which creates new cells.
Interphase
= a long growth period during which the cell grows and duplicates in preparation for the next
division:
- G 1 phase
the cell is at its smallest size, G 1 is a period of very active cell growth;
- S phase
the cell’s chromosomes are duplicated, growth continues at a slower pace;
- G 2 phase
the cell continues to grow slowly as it prepares for cell division.
Mitotic phase = nucleus and cytoplasm divide:
- Mitosis
the duplicated DNA is divided into two sets and the nucleus divides;
- Cytokinesis
the cytoplasm divides and two new cells, daughter cells, are formed.
G 0 = nongrowing, nondividing state.
Recap
Cell reproduction is required for growth and to replace cells throughout life. The cell cycle consists of
a long growth phase (interphase) during which the cell’s DNA is replicated and a shorter phase
(mitotic phase) during which the nucleus and the cell cytoplasm divide.
17.2 REPLICATION, TRANSCRIPTION AND TRANSLATION: AN OVERVIEW
DNA (deoxyribonucleic acid) = double stranded string of nucleotides intertwined into a helical shape.
Chromosomes = organize and arrange the DNA within the nucleus. (p. 407 fig. 17.2)
Gene = short segment of DNA that contains the code for one or more proteins.
RNA (ribonucleic acid) = single stranded.
Replication: Copying DNA before cell division
- Uncoiling of DNA helices
by DNA helicase.
- DNA polymerases
position and link new nucleotides.
- Centromere
the two chromatids remain attached at this single point.
Mutations are alternations in DNA
Mutation = alternations in DNA, resulting from mistakes during replication or chemicals or
physical forces.
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Mechanisms of DNA repair
DNA repair enzymes.
Transcription: Converting a gene’s code into mRNA
- Gene = expressed, when the protein for which it codes is produced;
- Transcription: converts the DNA code of a single gene into mRNA:
• Promotor
= unique base sequence which marks the beginning of every gene.
• RNA Polymerase
attaches to the promotor, starts the DNA unwinding process, assists in attaching
the RNA nucleotides.
• Primary transcript
= the RNA molecule transcribed form DNA = mRNA
is edited:
Introns (sections that do not carry useful genetic information) are left out,
exons (do carry genetic information) are left.
• Triplet code
three successive bases of mRNA (=codon) code for one amino acid.
Translation: Making a protein from RNA
Transfer RNA (tRNA)
= small molecules that carry the code for just one amino acid,
and an anticodon, a base triplet that is the complementary sequence to a codon of mRNA.
Ribosome
= consist of two subunits composed of rRNA (ribosomal RNA) and proteins, it has binding sites for
both mRNA and tRNA and contains the enzymes that connect het amino acids together.
hold the mRNA and tRNA in place while joining the amino acids.
- Initiation
a smaller ribosomal subunit and tRNA move along the mRNA until they encounter a
“start” codon (AUG), at this point a larger ribosomal subunit joins to form the intact
ribosome, which holds the mRNA in place while the tRNAs bring amino acids to it;
- Elongation
chain of amino acids lengthens;
- Termination
“stop” codon no anticodon correspond to it, so the peptide chain detaches from the
mRNA.
Recap
Before a cell divides, its DNA is replicated. During replication the two strands of DNA unwind and
separate from each other. Enzymes called DNA polymerases add new nucleotides to each of the
original strands, producing two complete molecules of DNA from one. Mutations may result from
mistakes in DNA replication or from physical or chemical damage. Repair mechanisms remove and
replace damaged DNA, if possible, before replication. During transcription, short portions of DNA
representing single genes are converted into a readable and transportable mRNA code. Translation is
a three-step process (initiation, elongation and termination) by which proteins are assembled from
amino acid building blocks according to an mRNA code. Assembly takes place on ribosomes.
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17.3 CELL REPRODUCTION: ONE CELL BECOMES TWO
Mitosis: Daughter cells are identical to the parent cell
= division of the nucleus (p. 414 fig. 17.9!!)
- Prophase
begins when the duplicated chromosomes become first visible.,
Mitotic spindle = parallel arrangement of microtubules.
- Metaphase
the duplicated chromosomes align on one plane at the center of the cell.
- Anaphase
the duplicate DNA molecules separate and move toward opposite sides of the cell.
- Telophase
begins when the two sets of chromosomes arrive at opposite poles of the cell.
Cytokinesis divides one cell into two identical cells
= division of the cytoplasm.
Mitosis produces diploid cells and meiosis produces haploid cells
- Diploid
46 chromosomes in 23 pairs, created by mitosis;
- Haploid
one set of 23 chromosomes, created by meiosis.
Meiosis: Preparing for sexual reproduction
- Meiosis 1
The precursor cell undergoes a typical S phase of interphase in which the DNA is
replicated.
• During prophase of meiosis 1, crossing-over may occur.
• The homologous pairs of chromosomes are separated from each other,
not the duplicates of each pair.
- Meiosis 2
proceeds like mitosis, except that the chromosomes are not duplicated again, the
chromosomes line up and the sister chromatids are separated from each other.
P. 416 fig. 17.11!!
- Crossing-over
= duplicated chromosomes pair up and swap sections of DNA
new recombination of the genes,
so none of the four haploid daughter cells are exactly alike!
Sex differences in meiosis: Four sperm versus one egg
p. 417 fig 17.12!!
Recap
Mitosis is a four-phase process in which the cell nucleus divides into two nuclei. The duplicated
chromosomes become visible in prophase, align along the center of the cell in metaphase, are pulled
apart in anaphase and move to opposite sides of the cell and become surrounded by new nuclear
membranes in telophase. During cytokinesis the cell divides into two cells, each containing a nucleus.
Meiosis is a two-step process in which the nucleus and cell divide twice, producing sperm or eggs
with the haploid number of chromosomes. Crossing-over ensures that the sperm and eggs are
genetically different from each other.
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17.4 HOW CELL REPRODUCTION IS REGULATED
Cell reproduction is controlled by cyclic fluctuations in the concentrations of proteins called cyclins.
They activate certain regulatory proteins that initiate specific events within the cell, e.g. DNA
replication.
It can also be influenced by conditions outside of the cell.
Recap
An internal cyclic control mechanism regulates the cell cycle. The cycle can be stopped at certain
checkpoints by internal surveillance systems and is influenced by conditions outside the cell.
17.5 ENVIRONMENTAL FACTORS INFLUENCE CELL DIFFERENTIATION
Differentiation
= the process by which a cell becomes different from its parent or sister cell.
Differentiation during early development
- Cells on the inside are exposed to another environment than cells on the surface.
activate different genes, leading to different developmental pathways.
- Clone
= make copies of an organism,
possible by “embryo splitting” (=splitting the eight-cell ball).
Differentiation later in development
- Each cell is shaped by
• Developmental history of the cells that came before it;
• Local environment.
- Substances that harm a fetus:
• Cigarette smoke;
• Alcohol;
• Medication;
• Illegal drugs;
• Chemicals in air, water and soil;
• Radiation.
Recap
Differentiation is the process whereby cells become different from each other. During early
development, environmental influences trigger differentiation. Some genes are expressed only at
certain stages of development, so genetic mutations during early development can be particularly
damaging. In adults, hundreds of different genes may be expressed by various types of cells.
17.6 CLONING AN ORGANISM REQUIRES AN UNDIFFERENTIATED CELL
17.7 THERAPEUTIC CLONING: CREATING TISSUES AND ORGANS
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18 CANCER: UNCONTROLLED CELL DIVISION AND DIFFERENTIATION
18.1 TUMORS CAN BE BENIGN OR CANCEROUS
- Hyperplasia
= substantial increase in the rate of cell division.
- Tumor
= discrete mass of rapidly dividing cells.
• Benign = goedaardig
• Cancerous.
18.2 CANCEROUS CELLS LOSE CONTROL OF THEIR FUNCTIONS AND STRUCTURES
- Dysplasia
= abnormal structural change.
- Cancerous tumor
= some of its cells lose all semblance of organization, structure and regulatory control;
• In situ cancer
entire tumor remains in one place;
• Malignant tumors
cancers that metastasize and cancer that invade normal tissues until they compromise
organ function.
Recap
Some tumors are benign, but when tumor cells change form dramatically and divide uncontrollably,
the tumor is called cancer. Cancer becomes malignant when cells invade and metastasize, starting
new tumors at distant sites.
18.3 HOW CANCER DEVELOPS (P. 434 FIG. 18.6)
• Cell must grow an divide uncontrollably;
• Cell must undergo physical changes that allow it to break away from surrounding cells.
Mutant forms of proto-oncogenes, tumor suppressor genes and mutator genes contribute
- Structural genes
code for the proteins necessary for cell growth, division, differentiation, cell adhesion.
- Regulatory genes
code for proteins that activate or repress the expression of the structural genes.
• Growth factors or growth inhibitors
• Proto-oncogenes
regulatory genes that promote cell growth, differentiation, division or adhesion.
oncogenes = mutated or damaged proto-oncogenes.
• Tumor suppressor genes
regulatory genes that inhibit cell growth, differentiation, division or adhesion.
- Mutator genes
are involved in DNA repair during replication,
mutated cell is vulnerable to errors in DNA replication and so, mutations.
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A variety of factors can lead to cancer
Carcinogen
= any substance or physical factor that causes cancer.
- Viruses and bacteria
If the viral sequence of DNA impairs the function of a normal gene, this will increase the
cancer risk.
- Chemicals in the environment
Some chemical carcinogens damage DNA directly, other increase the potency of other
carcinogens.
- Tobacco
most lethal carcinogen.
- Radiation
sun, radioactive radon gas…
- Diet
Certain fungi and plants produce carcinogens.
Obesity and excessive alcohol consumption are risk factor for cancer.
- Internal factors
Free radicals, highly reactive fragments of molecules that are produced by the body’s
biochemical processes.
The immune system plays an important role in cancer prevention
The immune system destroys mutated cells. Some cancers apparently can suppress the immune
system and others may have mechanisms for disguising themselves from attack.
Recap
Proto-oncogenes and tumor suppressor genes normally control the rate of cell division. Mutator
genes are involved in DNA repair. Mutations of any of these genes may contribute to cancer. Aside
from heritable susceptibility, factors that may contribute to the development of cancer include
viruses and bacteria, environmental chemicals, tobacco, radiation, dietary factors and alcohol. Free
radical created during cellular metabolism may also contribute to cancer. The immune system
normally protect us from cancer cells by killing them before they spread. Immune system
suppression allows cancers to develop more easily.
18.4 ADVANCES IN DIAGNOSIS ENABLE EARLY DETECTION
Tumor imaging: X-rays, PET and MRI
- X-rays
- PET: positron-emission tomography
- MRI: magnetic resonance imaging
Genetic testing can identify mutated genes
Enzyme tests may detect cancer markers
Telomerase is an enzyme rarely found in normal cells, but present in nearly all cancer cells.
Recap
Early diagnosis and prompt treatment of cancer are vital. Diagnostic techniques include X-rays,
positron-emission tomography (PET), magnetic resonance imaging (MRI), genetic testing and enzyme
markers.
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18.5 CANCER TREATMENT
Conventional cancer treatments: Surgery, radiation and chemotherapy
- Surgery
remove cancer cells in a specific region;
- Radiation
healthy cells recover more readily, but radiation therapy does injure or kill normal tissue;
- Chemotherapy
cytotoxic chemicals destroy cancer cells, but other fast dividing cells as well.
Magnetism and photodynamic therapy target malignant cells
- Magnetism
positioning a powerful magnet at the tumor site and injecting tiny metallic beads into the
patient’s bloodstream, the magnet pulls the beads into the tumor. The beads have been
coated with a chemotherapy drug, so they can kill the cancer cells.
- Photodynamic therapy
targeting cancer with light-sensitive drugs and lasers, laser light is focused on the tumor,
where it triggers a series of chemical events that kill malignant cells.
Immunotherapy promotes immune response
Immunotherapy attempts to boost the general responsiveness of the immune system so that it
can fight the cancer more effectively.
“Starving” cancer by inhibiting angiogenesis
Angiogenesis = growth of new blood vessels;
anti-angiogenic drugs can starve tumors by limiting their blood supply.
Molecular treatments target defective genes
Gene therapy: defective genes are repaired or replaced with their normal couterparts.
Recap
The mainstays of cancer treatments are surgery, radiation and chemotherapy. Recent advances
include magnetism, photodynamic therapy, immunotherapy, drugs to inhibit angiogenesis and
molecular treatments that focus on specific defective genes.
18.6 THE 10 MOST COMMON CANCERS
18.7 MOST CANCERS CAN BE PREVENTED
19 GENETICS AND INHERITANCE
20 DNA TECHNOLOGY AND GENETIC ENGINEERING
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21 DEVELOPMENT AND AGING
21.1 FERTILIZATION BEGINS WHEN SPERM AND EGG UNITE
The journey of egg and sperm
p. 487 fig. 21.1!!
One sperm fertilizes the egg
p. 487 fig. 21.2
- Fertilization
begins when the sperm’s nucleus enters the egg,
this triggers the release of enzymes from granules inside the egg, which make the
zona pellucida impenetrable to all other sperm.
- When the sperm nucleus enters it, the secondary oocyte completes meiosis and forms an
ovum.
Twins may be fraternal or identical
- Fraternal twins
arise from the ovulation of more than one oocyte in one cycle;
- Identical twins
arise from a single cell zygote, so they are genetically identical, which breaks in 2 groups.
Recap
Sperm deposited in the vagina must swim through the uterus and up the correct oviduct to meet the
egg. Fertilization begins when one sperm’s nucleus enters the oocyte and ends when the haploid
nuclei of sperm and egg fuse, creating a new diploid cell. Fraternal twins result from the fertilization
of two separate eggs. Identical twins occur when a single fertilized egg divides in to before
differentiation has begun.
21.2 DEVELOPMENT: CLEAVAGE, MORPHOGENESIS, DIFFERENTIATION AND GROWTH
Cleavage
= a series of cell divisions without cell growth or differentiation,
produces a ball of identical cells.
Morphogenesis
= the process of physical change, which occurs throughout development.
Differentiation
= individual cells begin to take on specialized forms and functions.
Growth
Growth of the zygote stars about the time that the organism becomes embedded in the
endometrial lining of the uterus and begins to receive nutrients from the mother.
Pregnancy is considered to compromise three periods called trimesters, each approximately three
months long, in which characteristics events take place.
Recap
The four processes associated with development are (1) cleavage, a series of cell divisions producing
a ball of identical cells; (2) morphogenesis, a sequence of physical changes; (3) differentiation, as cells
assume specialized forms and functions and (4) growth in size. Pregnancy is divided into three
trimesters.
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21.3 PRE-EMBRYONIC DEVELOPMENT: THE FIRST TWO WEEKS
Pre-embryo (many of the cells will be part of the placenta, not of the embryo.)
- Morula
= ball of about 32 identical cells, formed by successive cleavages of the zygote.
- Blastocyst
= a hollow ball comprising
• An outer sphere of cells, the trophoblast;
• A hollow central cavity;
• A group of cells, the inner cell mass
becomes embryo!
- Implantation
= the process by which the blastocyst becomes buried within the endometrium,
about day six or seven.
- Embryonic disk
(name of the cell mas after implantation), differentiates into ectoderm and endoderm.
marks end of pre-embryonic period!
(during the second week)
- Ectopic pregnancy
= the blastocyst implants outside the uterine cavity (buitenbaarmoederlijke zwangerschap).
Recap
During the pre-embryonic development, successive cleavages yield a morula. Early stages of
differentiation and morphogenesis cause the morula to become a blastocyst, which implants in the
lining of the uterus. The embryonic disk is destined to become the embryo.
21.4 EMBRYONIC DEVELOPMENT: WEEKS THREE TO EIGHT
Embryo
= the developing human from the beginning of week three until the end of week eight.
Tissues and organs derive from three germ layers:
- Ectoderm
Outermost layer, exposed to the amniotic cavity,
become skin, nervous system, hair, nails …
- Mesoderm
Middle layer,
become muscle, connective tissue and one, kidneys and ureters, bone marrow, testes or ovaries,
lining of blood vessels …
- Endoderm
Innermost layer,
becomes liver and pancreas, alveoli of the lungs, linings of the urinary bladder, urethra and
vagina, and several glands.
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Extra-embryonic membranes
- Amnion
= innermost layer, lines the amniotic cavity, filled with amniotic fluid,
which is derived from the mother’s interstitial fluid.
- Allantois
= temporary membrane that helps form blood vessels of the umbilical cord.
- Yolk sac
= small sac that hangs from the embryo’s ventral surface,
later becomes part of the fetal digestive tract and produces fetal blood cells.
- Chorion
= outermost layer, derived from the trophoblast,
forms structures that will be part of the exchange mechanism in the placenta.
Source of human chorionic gonadotropin (hCG)
= a hormone that supports pregnancy for the first three months
(until the placenta produces progesterone and estrogen.)
The placenta and umbilical cord
- Placenta
= entire structure that forms from the embryonic tissue and maternal tissue,
has a lot of important functions!
- Umbilical cord
= two-way life line that connects the placenta to the embryo’s circulation,
contains two arteries and one vein, which are considered part of the embryonic
circulation
arteries carry blood away from the embryonic heart, veins carry blood to the heart!
The embryo develops rapidly
- Two weeks
embryo is fully embedded in the endometrium, which provides nutrients,
the primitive streak appears.
- Three weeks
certain precursors to embryonic structures emerge,
neural groove of ectoderm forms, mesoderm separates into several segments (somites).
- Weeks five to eight
transition from a general vertebrate form to one that is recognizably human!
- Miscarriage
= spontaneous termination of pregnancy followed by expulsion of the embryo.
Recap
By the beginning of the embryonic development the embryo comprises three primary germ layers,
called the ectoderm, the mesoderm and endoderm, that ultimately give rise to fetal tissues and
organs. Four extra-embryonic membranes (amnion, allantois, yolk sac and chorion) serve varying
supportive functions. The placenta exchanges nutrients and gases between embryo and mother and
secretes hormones. The umbilical cord joins the embryo to the placenta. By the fifth week the
embryo is becoming distinctly human in form and by eight weeks it is an inch long (=2,54 cm).
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21.5 GENDER DEVELOPMENT BEGINS AT SIX WEEKS
Gender development begins at about six weeks.
The presence of an Y chromosome causes the embryo to start developing male characteristics :
the process begins when a gene on the Y chromosome, SRY is switched on.
It decodes for testis-determining factor, an protein that directs the initial development of the testes,
shortly after the testes start secreting testosterone, which stimulates further development.
The absence of a Y chromosome doesn’t trigger anything and the embryo becomes a female.
Recap
Gender development begins at about 6 weeks. The presence of a Y chromosome signals the embryo
to develop into a male, the absence of a Y chromosome causes the embryo to develop into a female.
21.6 FETAL DEVELOPMENT: NINE WEEKS TO BIRTH
Months three and four
- Kidneys develop sufficiently for the fetus to begin eliminating some wastes;
- Limbs are well developed, cartilaginous skeleton begins to be replaced by bone, teeth
form;
- Liver begins to function;
- Genitalia are well enough developed to determine sex.
- Liver and bone marrow begin producing blood cells during the fourth month
(formerly by the spleen.)
- Overall growth is rapid.
Months five and six
- Nervous system and skeletal muscles are sufficiently mature for the fetus to begin
moving, these movements are called quickening;
- Skin is covered by soft hair;
- Heartbeat is loud enough to be heard;
- Skeletal hardening continues.
- At six months, the fetus could survive outside the uterus.
Months seven through nine
period of continued rapid growth and maturation in preparation for birth:
- Eyes open and close spontaneously and can be conditioned to respond to
environmental sounds;
- Skin loses some of its reddish color and the soft hair;
- Both lungs and digestive systems are now ready.
Recap
The period of fetal development extends from nine weeks to birth at 38 weeks. Growth is rapid, with
the mature fetus weighing approximately 6-7,5 pounds at birth (=2,7 - 3,4 kg). The fetus begins to
move at about five months and life outside the womb is at least possible by about six months, when
the lungs begin to produce surfactant.
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21.7 BIRTH AND THE POSTNATAL PERIOD
Labor ends in delivery
The fetal pituitary gland releases ACTH,
which stimulates the adrenal gland to secrete steroid hormones,
that cause the placenta to increase estrogen and decrease progesterone production.
Estrogen stimulates production of prostaglandins + increases the number of oxytocin receptors.
stimulate the uterus to contract!
- Stage 1: Dilation
cervical opening widens, because of the pressure of the baby’s head,
breaking of the water, the amnion ruptures releasing the amniotic fluid.
- Stage 2: Expulsion
full cervical dilation allow the baby to pass through,
crowning, seeing the baby’s head at the labia,
after delivery the umbilical cord is clamped and cut.
- Stage 3: Afterbirth
Cesarean delivery: Surgical delivery of a baby
- Cesarean delivery
= C-section = incision made through the abdominal wall and uterus.
The transition from fetus to newborn
- Taking the first breath
- Changes in the cardiovascular system
Lactation produces milk to nourish the newborn
- Colostrum
= watery milk produces the first day after birth rich in antibodies, low in fat and lactose.
- Estrogen and progesterone
prepare the breast for lactation, but prevent the action of prolactin.
- Prolactin
stimulates milk production.
- Oxytocin
responsible for the contractions that deliver colostrum or milk, only when needed.
Recap
The period of labor and delivery is composed of three stages, dilation, expulsion and afterbirth. The
dilation phase may last 6-12 hours. At birth a sharp increase in carbon dioxide causes the newborn to
take the first breath. Shortly after birth, anatomical changes in the newborn route all blood through
the lungs. In the mother, prolactin stimulates lactation and oxytocin stimulates the release of milk
during suckling.
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21.8 FROM BIRTH TO ADULTHOOD
The neonatal period: A helpless time
- Nervous system and muscular system are relatively immature
movements are uncoordinated, weak and governed by reflexes rather than conscious
control.
- Doesn’t have enough strength to hold head up, must be supported.
- Eyes are open but are unable to focus.
- Are aware of and can respond to the environment,
but long-term memories can’t be retained.
- Digestive system is not ready for solid foods.
Infancy: Rapid development and maturation of organ systems
- Rapid change: e.g. triples in weight.
- Most of the growth occurs in the cerebral cortex:
sensory perception, motor function, speech and learning approve.
- First teeth appear at about six months.
- 14 months: walk on its own.
- Immune system lags behind others systems in its development.
Childhood: Continued development and growth
- Continued growth of all systems.
- Body form alters: long bones of the arms and legs lengthen.
- At the end of childhood, all organ systems are fully functional,
except the reproductive systems.
Adolescence: The transition to adulthood
- Rapid growth can lead to awkwardness and a temporary loss of coordination.
- Puberty
= maturation of the reproductive systems and the human sexual response.
- Brain is one of the last organs to reach full maturity.
Recap
Maturation of organ systems occurs at different rates. At birth, the neonate is physically helpless and
cannot form memories. Infants begin to eat solid foods and to walk. Brain growth is nearly complete
by the end of childhood. Muscle strength and coordination continue to improve throughout
childhood and the body changes to a more adult form. Adolescence is accompanied by a growth
spurt and by maturation of the reproductive systems.
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21.9 AGING TAKES PLACE OVER TIME
Aging
= the process of change associated with the passage of time.
Senescence
= the progressive deterioration of multiple organs and organ systems over time.
Longevity
= how long a person lives.
What causes aging?
Three differed hypotheses .
- An internal cellular program counts cell divisions
Telomeres
= disposable bits of DNA that do not code for any genes,
every time the DNA is replicated a telomere is removed.
When the cell runs out of telomeres, cell division begins to ‘eat away’ at vital genetic
information, eventually the cell stops dividing and dies.
- Cells become damaged beyond repair
Over time accumulated damage to DNA and errors in DNA replication become so great
that they can no longer be countered by the cell’s normal repair mechanisms.
- Aging is a whole-body process
Because the organs systems in a complex organism are interdependent, a decline in the
function of any one of them eventually impairs the function of the others.
Body systems age at different rates
- Musculoskeletal system and skin
Bone and muscle mass begin to decrease in early adulthood,
skin becomes thinner, less elastic and wrinkled.
- Cardiovascular and respiratory systems
Lung tissue becomes less elastic, decreasing lung capacity,
the heart walls become stiffer due to an increase in the ratio of collagen to muscle.
- Immune system
Thymus decreases, so there are fewer T cells,
activity (not number) of B cells declines as well,
higher rate of autoimmune disorders.
- Nervous and sensory systems
Neurons lost throughout life are not replaced,
brain and sensory function decline.
- Reproductive and endocrine systems
Woman: Menopause, the cessation of ovulation and menstruation.
Men: long, slow decline in the number of viable sperm.
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- Digestion and nutrition
Digestive system continues to function well,
some vitamins are not absorbed as efficiently, nutritional requirements decline.
Liver’s ability to detoxify and remove drugs declines significantly.
- Urinary system
Kidney mass declines, both blood flow and filtration rate fall.
• Men: prostate hypertrophy,
prostate presses against ureter, making urination difficult.
• Women:
incontinence due to a weakened urethral sphincter.
Aging well
Recap
Aging is a complex process that is still poorly understood. The number of times a cell can divide may
have an upper limit. In addition, damage may accumulate in cells until they no longer function
properly. All organs and organ systems decline in function with advancing age, though not
necessarily at the same rate. Even if the aging process cannot be stopped, it is certainly possible to
improve human health and wellness throughout life. Regular exercise and healthy nutrition are
important factors in aging well.
21.10 DEATH IS THE FINAL TRANSITION
Death
= irreversible cessation of circulatory and respiratory functions,
= irreversible cessation of all function of the entire brain, including the brain stem.
Recap
Death is the termination of life. Death starts with the failure of one or more critical organ systems
and ends ultimately with the inability to maintain an internal environment consistent with cellular
life.
22 EVOLUTION AND THE ORIGINS OF LIFE
23 ECOSYSTEMS AND POPULATIONS
24 HUMAN IMPACTS, BIODIVERSITY AND ENVIRONMENTAL ISSUES
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