2.68 Excretion

2.68 Understand how the kidney carries out its roles of excretion and of osmoregulation

Excretion

Chemical reactions in your body produce waste like carbon dioxide and urea. Urea contains nitrogen which is toxic and cannot be stored. Originally, urea was amino acids. They are used for growth, but excess amino acids must be removed since they are toxic.

1) Blood circulates to the liver. Amino acids are broken down and converted into urea (process of deamination).

2) Blood re-enters the bloodstream and goes to both of the kidneys. The kidneys will filter the urea from the blood. Water will be added to urea to form urine. Urine will drain down the ureter and will be collected in the bladder.

3) Filtered blood returns to the circulation without urea. 

Amino acids --> LIVER --> Urea --> (less toxic) --> Kidneys