2.68a Excretion

1. The role of the kidney in excretion, is the excretion of urea.
2. Urea is poisonous to the human body because it contains nitrogen.
3. The original form of the nitrogen is in our bloodstream as amino acids, which are used for growth, but if there are any in excess they have to be removed.
4. Blood cirulates into the liver, where the amino acids are broken down and converted into urea. This reenters the blood stream into both the kidneys.
5. The kidneys filter the urea from the blood, and add it with water to form urine and this flows down the uretus into the bladder.