2.68a Excretion

understand how the kidney carries out its roles of excretion and of osmoregulation

Both the liver and kidneys remove toxic amino acids and urea from the body by breaking the amino acids down into urea (in the liver) and converting the urea into urine (in the kidneys), finally excreting it out of the body through the bladder in the form of urine

Urea, contains nitrogen
Nitrogen toxic to body - unable to store

Amino acids - Normally used for growth
Excess amino acids must be excreted (liver and kidneys)

1. Liver
- Blood circulates to the liver
- Amino acids in blood broken down
- Converted into urea
- Returns to the bloodstream

2. Kidneys
- Blood circulates to both kidneys
- Kidneys filter urea from blood
- Urea added to water to form urine

- Urine flows down into the bladder via ureters
- Filtered blood returns to the bloodstream in veins without toxic amino acids and urea