1. The Urinary System
Chapter 37.3

2. Urinary System
Function: Helps maintain the homeostasis of body fluids.
Structure:
2 kidneys
2 ureters
1 urinary bladder
1 urethra

3. 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.

4. 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.

5. 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.

7. 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

8. 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