The Urinary System

Waste Products

Carbon dioxide – a waste product of cellular respiration is dumped into the blood stream and eventually removed by the lungs

Ammonia (NH3) is removed through water

This waste comes from the cells breakdown of old proteins

It is also what makes bleach smell so in high concentrations it is poisonous to the cells and must be removed

Removal of Ammonia

Once excreted into the blood stream by cells,

it is carried to the liver where it is converted

from ammonia into urea which is much less

toxic

It is then carried from the liver to the kidneys

where it is removed

The Hard-working Kidneys

The two kidneys in the body receive between

1100 – 2000 liters (1160 – 2100 quarts or

500 gallons) of blood per day – about the

volume of a car!

Because the body has only about 5.6 liters of

blood, your blood runs through the kidneys to

be cleaned about once every four minutes.

The Job of the Kidneys

They are responsible for cleaning the blood

by removing metabolic wastes, excess

solutes, and excess water and excreting

them as urine

Besides removing urea, it also removes

excess salts or glucose, the remnants of

drugs (reason for urine tests), and excess

water.

afferent arteriole

glomerulus

efferent arteriole

proximal

convoluted

tubule

distal

convoluted

tubule

Loop of Henle

blood

blood

The Nephron

Nephrons are connected to renal artery/vein and

ureter.

The kidney produces urine through 4 steps.

Ammonotelic (ammonia-excreting)

animals generally live only in aquatic

habitats, because ammonia is extremely

toxic, and a large volume of water is

required to maintain the excreted

ammonia level lower than the body level.

The release of ammonia occurs across

the gills of aquatic animals

Although ammonia excretion is

present in some forms in

mammals, the major nitrogenous

waste excreted is urea. Urea is

less toxic than ammonia, and

requires less water for elimination.

Therefore, ureotelic (urea-

excreting) animals are most often

terrestrial.

Land snails, insects, birds, and many

reptiles excrete uric acid as the main

nitrogenous waste.

Like urea, uric acid is relatively

nontoxic.

But unlike either ammonia or urea,

uric acid is largely insoluble in water

and can be excreted as a semisolid

paste with very little water loss.