Download The Urinary System

The Urinary System
Chapter 37.3
Urinary System
• Function: Helps maintain the
homeostasis of body fluids.
• Structure:
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2 kidneys
2 ureters
1 urinary bladder
1 urethra
The Kidney
• The kidneys are main organs of the urinary
system.
• Function:
– Filters and removes
waste from blood
– Regulates body water
volume, blood volume
and blood pressure
– Regulates the amount
of ions and salt in
the body.
– Produces urine.
• Protein is broken down for energy in the
body– this releases ammonia (very toxic)
• Ammonia is converted into urea by the
liver (less toxic)
• Some of the urea is removed by the skin
in perspiration (sweating). Most is
removed from the blood by the kidneys.
Waste is removed in the kidney by Nephrons.
• 1 million nephrons per kidney
• Blood entering the nephron carries water,
glucose, salt, vitamins, amino acids, ions,
urea and waste.
• 1st step is filtration
– Small molecules, salt and water, and other
waste are removed from the blood.
• 2nd step is reabsorption
– Important material (water, glucose, and salt)
are reabsorbed into the blood.
The remaining fluid is urine.
• Urine is water and solutes.
– Solutes = excess elements,
ions, salt, and vitamins,
urea, toxic substances and
drugs
• Approx. 1-2 Liters of urine
produced a day.
• Ureters
– Carries urine from the
kidneys to the bladder.
– About 25 cm long
• Urinary Bladder
– Stores the urine
– Muscular sac on the bottom of the pelvic
cavity.
– Average volume = ½ Liter
– Max capacity = ¾ Liter
• Urethra
– Passes urine out of the body
– Female approx 3-4 cm
– Male approx 18 cm