Anatomy Notes 9 The Excretory System - Hart High School

The Excretory System
Chapter 38-3
Waste Removal
• A. EXCRETION refers to the removal of
metabolic wastes from the body.
• B. The main types of waste that your body
must discard are UREA, and URIC ACID.
Both waste products contain Nitrogen.
• C. If not removed, waste will accumulate in
the cells and cause toxicity (poisoning),
TISSUE death and nutrient starvation.
• i. OXYGEN and GLUCOSE cannot effectively move
into a cell full of nitrogenous wastes.
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Your Kidneys
• A. Your kidneys are the organs responsible
for filtering waste products from your blood.
Without a kidney (or substitute), you would
die from wastes and actually DROWN in
excess body fluids in a period of about 3-4
days.
• B. The kidneys are located in the small of the
BACK, one behind the stomach, and the other
behind the liver.
Your Kidneys
• C. There are
several regions of
the kidney:
• a. CORTEX: outer
area of the kidney
• b. MEDULLA: middle
area of the kidney
• c. RENAL PELVIS:
inner region with
collecting ducts for
urea
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Your Kidneys
• D. Blood enters the
kidney through the
RENAL ARTERY, and
leaves through the
RENAL VEIN. The
renal artery
transports nutrients
to the kidney for use
and waste to the
kidney for filtration.
Your Kidneys
• E. NEPHRONS are tiny filters in each kidney
(here is where URINE is made). There are
roughly one MILLION per kidney and they are
made up of the following parts:
• a. BOWMAN’S CAPSULE: encloses a bed of capillaries;
blood from capillaries is pushed through Bowman’s
capsule for filtration
• b. GLOMERULUS: capillary bed; gets blood from renal
artery
• c. RENAL TUBULE: wastes travel through this tube
• i. Renal tubule consists of 3 parts including the LOOP OF
HENLE. This structure helps COLLECTING DUCTS reabsorb
any water that might be mixed in the waste by keeping a high
NaCl concentration outside the ducts so that osmosis can
occur.
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The Nephron
The Filtration Process
(How your kidneys maintain homeostasis)
• A. Blood enters the kidney through the RENAL
ARTERY which breaks down into arterioles in the
cortex.
• B. Capillaries end in the GLOMERULUS which is
nicely fitted into Bowman’s Capsule. Water, waste,
glucose, and salts are forced into the Bowman’s
Capsule by high pressure (this is where the
FILTRATION process takes place)
• C. Some of the filtrate must be taken back by
osmosis of active transport into the CIRCULATORY
system because is contains “good stuff.”
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The Filtration Process
(How your kidneys maintain homeostasis)
• D. The URINE (fluids and wastes including
urea) collects in collecting ducts. From
there it moves through the URETER (a tube
for urine transport) and is stored in the
BLADDER until it is too full and contracts.
At that point urine leaves the bladder
through the URETHRA.
The Filtration Process
(How your kidneys maintain homeostasis)
• i. Did you know that your urine is sterile? Unless you
have a bodily infection, your urine should be clean of
bacteria or viruses. You can use it as an emergency
antiseptic (think “Survivor”), and some people still
think urine has healing value (yes, they drink it and
make medicines out of it). GROSS!
• ii. If your kidneys are failing their filtration duties, you
may need mechanical kidney filtration called DIALYSIS.
• iii. A fairly common kidney disorder is KIDNEY
STONES. Kidney stones are made of CRYSTALLIZED
UREA. They are extremely painful and should be
treated by a doctor. Treatment may include letting the
stone pass, surgery, or electrical shock to break up the
stone.
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Excretory System
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