Lect3.pdf

LE 41-23
Muscle layers
Villi
Intestinal wall
Vein carrying blood
to hepatic portal
vessel
Blood
capillaries
Epithelial
cells
Large
circular
folds
Villi
Key
Nutrient
absorption
Lymph
vessel
Lacteal
Microvilli
(brush border)
Epithelial cells

• Each villus contains a network of blood vessels and a
small lymphatic vessel called a lacteal

• Amino acids and sugars pass through the epithelium of the
small intestine and enter the bloodstream (through hepatic
portal vein)
• After glycerol and fatty acids are absorbed by epithelial
cells, they are recombined into fats within these cells
• These fats are mixed with cholesterol and coated with
protein, forming molecules called chylomicrons, which are
transported into lacteals

LE 41-24
Bile salts
Fat droplets
coated with
bile salts
Epithelium
of small
intestine
Epithelium
of lacteal
Fat globule
Micelles made
up of fatty acids,
monoglycerides,
and bile salts
Lacteal

The Large Intestine
• The large intestine, or colon, is connected to
the small intestine
• Its major function is to recover water that
has entered the alimentary canal
• Wastes of the digestive tract, the feces,
become more solid as they move through
the colon
• Feces pass through the rectum and exit via
the anus

• The colon houses strains of the bacterium
Escherichia coli, some of which produce vitamins

Evolutionary adaptations of
vertebrate digestive systems are
often associated with diet
• Digestive systems of vertebrates are
variations on a common plan
• However, there are intriguing
adaptations, often related to diet

Some Dental Adaptations
• Dentition, an animal’s assortment of teeth, is one
example of structural variation reflecting diet
• Mammals have specialized dentition that best
enables them to ingest their usual diet

LE 41-26
Incisors
Canines
Carnivore
Herbivore
Omnivore
Premolars
Molars

Stomach and Intestinal
Adaptations
• Herbivores generally have longer alimentary canals
than carnivores, reflecting the longer time needed to
digest vegetation

LE 41-27
Small
intestine
Stomach
Cecum
Colon
(large
intestine)
Carnivore Herbivore
Small intestine

Symbiotic Adaptations
• Many herbivores have fermentation
chambers, where symbiotic microorganisms
digest cellulose
• The most elaborate adaptations for an
herbivorous diet have evolved in the animals
called ruminants

LE 41-28
Intestine Rumen
Abomasum
Esophagus
Omasum
Reticulum

Gastrovascular Cavities
• Simple animals, such as cnidarians, have a body
wall only two cells thick that encloses a
gastrovascular cavity
• This cavity functions in both digestion and
distribution of substances throughout the body
• Some cnidarians, such as jellies, have elaborate
gastrovascular cavities

LE 42-2
Mouth
Circular
canal
Radial canal
5 cm

Open and Closed Circulatory
Systems
• More complex animals have either open or
closed circulatory systems
• Both systems have three basic components:
– A circulatory fluid (blood or hemolymph)
– A set of tubes (blood vessels)
– A muscular pump (the heart)

• In insects, other arthropods, and most
molluscs blood bathes the organs
directly in an open circulatory system
• There is no distinction between blood
and interstitial fluid, and this general
body fluid is more correctly called
hemolymph

LE 42-3
Anterior
vessel
Lateral
vessel
Ostia
An open circulatory system.
Heart
Hemolymph in sinuses
surrounding organs
Tubular heart
Interstitial
fluid
Dorsal vessel
(main heart)
Auxiliary hearts Ventral vessels
A closed circulatory system.
Heart
Small branch vessels
in each organ

• In a closed circulatory system, blood is
confined to vessels and is distinct from the
interstitial fluid
• Closed systems are more efficient at
transporting circulatory fluids to tissues and
cells

LE 42-4
FISHES
Gill capillaries
Artery
Gill
circulation
Heart:
Ventricle (V)
Atrium (A)
Vein Systemic
circulation
AMPHIBIANS
Lung and skin capillaries
Pulmocutaneous
circuit
V
Right
Systemic
circuit
Left
Systemic capillaries Systemic capillaries
A
A
REPTILES (EXCEPT BIRDS)
Right
systemic
aorta
Lung capillaries
Pulmonary
circuit
Left
A
A systemic
V
V
aorta
Right Left
Systemic capillaries
Systemic circuits include all body tissues except lungs. Note that circulatory systems are depicted
as if the animal is facing you: with the right side of the heart shown at the left and vice-versa.
MAMMALS AND BIRDS
A
Lung capillaries
Pulmonary
circuit
A
V
V
Right Left
Systemic
circuit
Systemic capillaries

LE 42-5
Anterior
vena cava
Pulmonary
artery
Capillaries
of right lung
Pulmonary
vein
Right atrium
Right ventricle
Posterior
vena cava
Aorta
Capillaries of
head and
forelimbs
Pulmonary
artery
Capillaries
of left lung
Pulmonary
vein
Left atrium
Left ventricle
Aorta
Capillaries of
abdominal organs
and hind limbs

LE 42-6
Pulmonary artery
Anterior
vena cava
Right
atrium
Pulmonary
veins
Semilunar
valve
Atrioventricular
valve
Posterior
vena cava
Right
ventricle
Left
ventricle
Aorta
Pulmonary
artery
Left
atrium
Pulmonary
veins
Semilunar
valve
Atrioventricular
valve

• The heart contracts and relaxes in a rhythmic
cycle called the cardiac cycle
• The contraction, or pumping, phase is called
systole
• The relaxation, or filling, phase is called diastole

To adjust blood pressure independently in the
capillaries of the gas-exchange surface and in
the capillaries of the general body circulation, an
organism would need
– A. an open circulatory system.
– B. a hemocoel.
– C. a lymphatic system.
– D. a two-chambered heart.
– E. a four-chambered heart.

LE 42-7
AV valves
open
Atrial and
ventricular
diastole
Semilunar
valves
closed
0.4 sec
0.1 sec
0.3 sec
AV valves
closed
Atrial systole;
ventricular
diastole
Semilunar
valves
open
Ventricular systole;
atrial diastole

• The heart rate, also called the pulse, is
the number of beats per minute
• The cardiac output is the volume of
blood pumped into the systemic
circulation per minute

Maintaining the Heart’s Rhythmic
Beat
• Some cardiac muscle cells are selfexcitable,
meaning they contract without
any signal from the nervous system

• The sinoatrial (SA) node, or pacemaker,
sets the rate and timing at which cardiac
muscle cells contract
• Impulses from the SA node travel to the
atrioventricular (AV) node
• At the AV node, the impulses are delayed
and then travel to the Purkinje fibers that
make the ventricles contract

• Impulses that travel during the cardiac
cycle can be recorded as an
electrocardiogram (ECG or EKG)

LE 42-8
Pacemaker
generates wave of
signals to contract.
SA node
(pacemaker)
ECG
AV
node
Signals are delayed
at AV node.
Signals pass
to heart apex.
Bundle
branches Heart
apex
Purkinje
fibers
Signals spread
throughout
ventricles.

• The pacemaker is influenced by nerves,
hormones, body temperature, and exercise

Concept 42.3: Physical principles
govern blood circulation
• The physical principles that govern movement
of water in plumbing systems also influence
the functioning of animal circulatory systems

Blood Vessel Structure and
Function
• The “infrastructure” of the circulatory
system is its network of blood vessels
• All blood vessels are built of similar
tissues and have three similar layers

LE 42-9
Artery
Endothelium
Smooth
muscle
Connective
tissue
Artery Vein
Endothelium
Capillary
100 µm
Basement
membrane
Endothelium
Smooth
muscle
Connective
tissue
Arteriole Venule
Vein
Valve

• Structural differences in arteries, veins,
and capillaries correlate with functions
• Arteries have thicker walls that
accommodate the high pressure of
blood pumped from the heart

• In the thinner-walled veins, blood flows
back to the heart mainly as a result of
muscle action

LE 42-10
Direction of blood flow
in vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)

Blood Flow Velocity
• Physical laws governing movement of fluids
through pipes affect blood flow and blood
pressure
• Velocity of blood flow is slowest in the
capillary beds, as a result of the high
resistance and large total cross-sectional
area