• Components of urinary system are:
– 2 kidneys
– 2 ureters
– Urinary bladder
– urethra

• Kidneys supplied by renal arteries , drained by renal veins
• The kidneys remove waste from the blood through excretion of urine. The urine is transported passively to the ureters, urine carried down the ureters to urinary bladder by
peristalisis and gravitational forces.

• Surrounded in a packing of fat – for protection
• Located against posterior wall of abdominal cavity
• Functional unit of the Kidney is called the nephron, ~1,000,000 per Kidney.
• Micturition = urination – the process of eliminating urine from the body
• Cap like structures called Adrenal Glands sit on top of each Kidney

1. Elimination of Nitrogenous Wastes
2. Regulation of fluid/electrolytes – also called osmoregulation
3. pH regulation
4. Blood chemical composition (ex. Sugar)
– Hyperglycemia – condition which can result if
BSL (blood sugar level) is TOO high
– Hypoglycemia – when BSL is TOO LOW – causes weakness, fainting, or unconsciousness

5. Regulation of RBCs
6. Regulation of Blood Pressure

• Ammonia, Uric Acid, Urea
• Nitrogenous wastes are produced from catabolism (breakdown) of proteins
• Proteins  Amino Acids  Ammonia
(hydrolysis or digestion) Deamination (type of break down)

3
• Ammonia
– Highly toxic
– Large amounts of water needed to dilute ammonia – so it can be safely excreted
– Very soluble in water
– Excreted by: fish
– Can be converted into either uric acid or urea

• Uric Acid
– Produced from ammonia – requires energy to make
– Is white, insoluble in water, crystals
– Minimal water required for excretion
– Excreted by birds and reptiles - bird pee = white paste
– The least toxic forms of Nitrogenous wastes

• Urea
– Main nitrogenous waste
– Produced in liver from ammonia (NH
3
)
– Highly soluble in water
– Travels in blood into the kidneys – filtered out to make urine
– Excreted: by mammals
– Medium toxicity
– Needs medium amount of water to dilute so it can safely move through the excretory organs for disposal

H - N – H
|
H
Least Complex
LEAST
MOST
2 NH
3
+ CO
2
Most Complex
MOST
LEAST

• Compare and Contrast – Three nitrogenous waste products – Ammonia – Uric Acid – Urea
• Q 1- 4 p 302 of Text Book