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38–3 The Excretory System
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2. Functions of the Excretory System
Every cell produces metabolic wastes.
The process by which these wastes are eliminated is called excretion.
The skin excretes excess water and salts in the form of sweat.
The lungs excrete carbon dioxide.
The kidneys also play a major role in excretion.
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3. Functions of the Excretory System
The kidneys:
remove waste products from the blood.
maintain blood pH.
regulate the water content of the blood and, therefore, blood volume.
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The Kidneys
The kidneys are located on either side of the spinal column near the lower back.
The functional blood-filtering unit of the kidney is called a nephron.
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The Kidneys
A tube, called the ureter, leaves each kidney, carrying urine to the urinary bladder.
The urinary bladder is a saclike organ where urine is stored before being excreted.
Urine is excreted through the urethra - a tube leading from the bladder to the outside of the body.
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The Kidneys
Structure of the Kidneys
Kidney
Nephron
Kidneys are made up of nephrons. Blood enters the nephron, where impurities are filtered out and emptied into the collecting duct. The purified blood leaves the nephron through the renal vein.
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The Kidneys
“Dirty” blood enters the kidney through the renal artery & it removes urea, excess water, and other waste products and passes them to the ureter.
The clean, filtered blood leaves the kidney through the renal vein and returns to circulation.
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The Kidneys
Cortex
Medulla
Renal artery
Renal vein
Ureter
To the bladder
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The Kidneys
The functional units of the kidney are called nephrons.
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The Kidneys
As the kidney works, purified blood is returned to circulation while urine is collected in the urinary bladder.
Urine is stored here until it is released from the body through a tube called the urethra.
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Kidney Disorders
Kidney Disorders
Humans have two kidneys, but can survive with only one.
If both kidneys are damaged by disease or injury, there are two options:
a kidney transplant
kidney dialysis
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Kidney Disorders
Kidney Dialysis
Blood in tubing flows through dialysis fluid
Blood pump
Vein
Artery
Shunt
Used dialysis fluid
For people with damaged kidneys, dialysis machines can perform many of the functions of the kidneys.
Dialysis machine
Fresh dialysis fluid
Compressed air
Air detector
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38–3
A dialysis machine performs the function of which structure in the excretory system?
nephron
ureter
urethra
glomerulus
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38–3
In the human body, the kidneys play an important role in
producing digestive enzymes.
circulating the blood.
destroying old red blood cells.
maintaining homeostasis.
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38–3
Urine leaves the body through the
loop of Henle.
glomerulus.
urethra.
bladder.
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