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Section 10.3 Your Excretory System
Your Excretory System
Objectives
Identify the organs of excretion in the body and
their functions.
Explain how the kidneys remove wastes from
the blood and produce urine.
Describe behaviors that can keep your
excretory system healthy.
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Section 10.3 Your Excretory System
Health Stats This graph compares the amount of water you excrete in
sweat and urine on a normal day and on a hot day.
In a paragraph, discuss how weather affects water loss.
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Section 10.3 Your Excretory System
Organs of Excretion
• Excretion is the process by which the body collects
and removes wastes.
• Several organs in the body are involved in waste
collection and removal
• liver
• lungs
• skin
• kidneys
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Section 10.3 Your Excretory System
Liver
• The liver converts impurities and poisons in the body to
less harmful substances.
• The liver forms urea from a harmful waste product of
protein breakdown.
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Section 10.3 Your Excretory System
Lungs and Skin
• The lungs remove carbon dioxide and some water
from the body.
• Sweat glands in the skin serve an excretory function
because water and urea are excreted in perspiration.
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Section 10.3 Your Excretory System
Kidneys
• The kidneys, which are the major organs of the
excretory system, filter urea and other wastes from the
blood.
• You have two kidneys, each about the size of a fist.
• Urine is a watery fluid produced by the kidneys that
contains urea and other wastes.
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Section 10.3 Your Excretory System
The Excretory System
Kidney
The kidneys produce urine by
filtering urea and other wastes
from the blood.
Ureter
One ureter extends from each
kidney. The ureters carry urine
from the kidneys to the bladder.
Bladder
The bladder is a saclike
muscular organ that
stores urine.
Urethra
Urine travels through the
urethra as it exits the body.
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Section 10.3 Your Excretory System
Filtration of Wastes
• Each kidney contains about a million nephrons, tiny
filtering units that remove wastes and produce urine.
• The nephrons filter wastes in stages.
• Needed materials and wastes are filtered from
the blood.
• Most needed materials are returned to the blood,
and the wastes are eliminated from the body.
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Section 10.3 Your Excretory System
Filtering Out Wastes
• Blood enters the kidneys.
• Blood flows through smaller blood vessels until it
reaches a cluster of tiny blood vessels in a nephron
called a glomerulus (gloh MUR yoo lus).
• Urea, salts, glucose, and water are filtered from the
glomerulus into a thin-walled capsule.
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Section 10.3 Your Excretory System
Formation of Urine
• As the filtered material flows through the tube, the
glucose, most of the water, and other needed materials
pass from the tube back into the blood.
• Urea and other wastes, such as excess vitamins and
harmful substances, stay in the tube.
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Section 10.3 Your Excretory System
A Nephron
Blood flows from an artery into a nephron.
In the glomerulus, urea, water, glucose,
and other materials are filtered from the
blood. These materials pass into a capsule
that surrounds the glomerulus.
The materials pass from the capsule
into a long, twisting tube. The tube
is surrounded by blood vessels.
As the filtered material flows
through the tube, most of the
water and glucose are reabsorbed
into the blood. Most of the urea
and other waste stay in the tube.
After the reabsorbing process is
complete, the liquid that remains
in the tube is called urine.
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Section 10.3 Your Excretory System
For: Updates on the excretory system
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Section 10.3 Your Excretory System
Keeping Healthy
To help your kidneys function at their best, it is
important to drink plenty of water and to see a doctor if
you have symptoms of an infection.
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Section 10.3 Your Excretory System
Drinking Water
Because many of the
waste products filtered by
your kidneys are harmful,
it is best if they are
diluted as much as
possible.
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Section 10.3 Your Excretory System
Treating Infections
• Urinary tract infections, which are bacterial infections of
the urethra or bladder, are common disorders.
• Symptoms of urinary tract infections include frequent,
painful urination and blood in the urine.
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Section 10.3 Your Excretory System
Preventing Kidney Stones
• Kidney stones are pebblelike masses of salts, and often
calcium, that form in the kidneys.
• Drinking plenty of fluids and eating a diet that is low in
salt may reduce your risk of developing kidney stones.
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Section 10.3 Your Excretory System
Treating Kidney Failure
• Kidneys that are damaged from an injury, diabetes,
uncontrolled high blood pressure, or other diseases
may fail.
• Kidney failure can be treated by dialysis.
• During dialysis, a machine is used to filter blood in
place of the kidneys.
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Section 10.3 Your Excretory System
Vocabulary
excretion
The process by which the body collects and
removes wastes.
urea
A substance formed in the liver from a waste
product of protein breakdown.
kidney
A major organ of excretion that filters wastes
from the blood and produces urine.
urine
A watery fluid containing urea and wastes that is
excreted from the body.
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Section 10.3 Your Excretory System
Vocabulary
nephron
A tiny filtering unit in the kidney that removes
wastes and produces urine.
glomerulus
A cluster of tiny blood vessels in a nephron.
dialysis
A treatment for kidney failure in which a
machine is used to filter wastes from blood.
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Section 10.3 Your Excretory System
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Section 10.3 Your Excretory System
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Section 10.3 Your Excretory System
End of Section 10.3
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