Human Excretory System
Human metabolic waste includes carbon dioxide, water,
salts, and urea. These wastes pass from the cells into the
blood and are carried to the excretory organs that expel them
from the body.
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Lungs
The lungs function in the excretion of carbon
dioxide and water vapor, which are wastes from
cellular respiration.
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Liver
•The liver gets rid of
excess amino acids
•The amino acids are
converted into urea
•The kidneys excrete the
urea
•The liver also breaks
down old red blood cells
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Skin and Sweat Glands
•Sweat glands excrete water,
salts, and some urea.
•These wastes diffuse from the
capillaries into the sweat glands
and then through ducts to pores
on the surface of the skin.
•This mixture of wastes and
water is excreted by perspiration
(sweat).
•Perspiration functions primarily
to regulate body temperature.
•Evaporation of sweat cools the
body and is another example of
how the body maintains
homeostasis.
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Kidney
•Human kidneys remove urea from blood and regulate the
concentrations of most substances found in body fluids.
•Blood is carried to each kidney through an artery.
•Within the kidney the artery divides into small balls of
capillaries called glomeruli (glomerulus-singlular).
•Each glomerulus is part of a nephron.
•A nephron is the functional unit of a kidney.
•There are over 1 million nephrons in a kidney.
•A nephron is a glomerulus surrounded by a cup-shaped
structure called Bowman’s Capsule.
•The Bowman’s Capsule is surrounded by capillaries.
•As blood flows through the glomerulus, water, salts, and
glucose diffuse out into the Bowman’s Capsule. This is
filtration. The fluid that is not diffused out is urine.
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Urine passes through the nephron tubules into the ureter.
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Dialysis:
• When a set of kidneys
don't do their job, their
owner has what is called
a chronic kidney
condition. Eventually,
those kidneys may be
considered failing. Much
like a filter system hooked
up to a pool, dialysis
gives the kidneys a break
by skimming waste for
them.
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•Urine flows from each
kidney into a tube called
the ureter
•The ureters carry the
urine to the bladder,
where it is stored
temporarily
•Urine is expelled from
the bladder into a tube
called the urethra
•The urethra leads to
the outside of the body
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