Transcript Prentice Hall Biology - Valhalla High School

Interest Grabber
Section 38-3
Your Body’s Filter
Have you ever seen a water-purification system attached to a faucet?
This system removes impurities from the water such as arsenic or other
chemicals that can be harmful to people. As water passes through the
filters contained in the system, the impurities are trapped on the surface of
the filters. Eventually, the water that comes out of this purifier is free of the
impurities.
1. Your body has its own system for filtering blood. Why might the blood
in your body need to be filtered?
2. What organ(s) do you think filters your blood?
3. How do you think the filtered materials leave your body?
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Section:
Section Outline
Section 38-3
38–3
The Excretory System
A. Functions of the Excretory System
B. The Kidneys
1. Kidney Structure
2. Filtration
3. Reabsorption
4. Kidney Stones
C. Control of Kidney Function
D. Homeostasis by Machine
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Section:
Functions of the Excretory System
•Every cell in the body produces metabolic wastes as a result of
maintaining homeostasis
– Wastes such as urea, excess salts and carbon dioxide must be
removed from the body
•The skin, lungs and liver are three organs that assist in excretion
– The skin excretes excess salts, water and a small amount of urea
– The lungs excrete carbon dioxide
– The liver takes excess amino acids from the blood stream and
converts them to useful compounds
• In the process of conversion, poisonous nitrogen compounds
are created, which are turned into urea
• Urea is then removed from the bloodstream by the body’s
principal organs of excretion – the kidneys
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Section:
Kidneys
•The kidneys have many roles
– Remove waste products from the blood
– Maintain blood pH
– Regulate the water content of the blood and therefore blood volume
•As waste-laden blood enters the kidney from the renal artery, it removes
urea, excess water and other wastes and passes them to the ureter
•The clean, filtered blood leaves the kidney through the renal vein and
returns to circulation
Go to
Section:
The Urinary System
Section 38-3
Vein
Kidney (Cross Section)
Kidney
Cortex
Medulla
Ureter
Urinary bladder
Urethra
Go to
Section:
Artery
Figure 38–17 Structure of the Kidneys
Section 38-3
Kidney
Nephron
Bowman’s
capsule
Cortex
Capillaries
Glomerulus
Medulla
Renal
artery
Renal vein
Ureter
Collecting
duct
Vein
To the bladder
Artery
Loop of Henle
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Section:
To the ureter
The Nephron
Section 38-3
Reabsorption
Filtration
Most filtration occurs in the
glomerulus. Blood pressure forces
water, salt, glucose, amino acids,
and urea into Bowman’s capsule.
Proteins and blood cells are too
large to cross the membrane; they
remain in the blood. The fluid that
enters the renal tubules is called
the filtrate.
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Section:
As the filtrate flows through the
renal tubule, most of the water
and nutrients are reabsorbed into
the blood. The concentrated fluid
that remains is called urine.
Control of Kidney Function
•The activity of the kidneys is controlled by the blood itself.
•Water is absorbed into the blood from the digestive system.
– The concentration of water in the blood increases.
• Without your kidneys, the increase in water conc. would force
water into cells and tissues, causing your body to swell
– As the amount of water in the blood increases, the rate of water
reabsorption in the kidneys decreases.
• Less water is returned to the blood and the excess water is sent
to the bladder.
•With an increase in salt, your kidneys return less salt to the blood, and
send the excess salt to the bladder.
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Section:
Disease
•Kidney Stones
– Substances such as calcium, magnesium or salts in the urine
crystallize and form stones
– These stones may block the ureter, causing great pain
– Often treated using ultrasound waves
• The stones gets pulverized into smaller fragments, which are
then excreted in the urine.
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Section:
Homeostasis by Machine
•Dialysis
– Blood is removed from the body through a tube and pumped
through special tubing that acts like nephrons
– Wastes diffuse out of the blood and into a fluid-filled chamber
– The purified blood is then returned to the body
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Section:
Figure 38–19 Kidney Dialysis
Section 38-3
Blood in tubing flows
through dialysis fluid
Blood pump
Vein
Artery
Used dialysis fluid
Shunt
Air detector
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Section:
Dialysis
machine
Fresh
dialysis
fluid
Compressed
air
Video 2
Kidney Function
Click the image to play the video segment.