Sunday, October 30, 2011

(I)GCSE 2.68 a) Excretion



How kidneys carry out its roles of excretion and osmoregulation.

- Urea contains Nitrogen which is toxic to the body and cannot be stored. 
- The original form of Nitrogen circulating in our blood stream are the Amino Acids.
- Amino acids are normally used for growth but extra amino acids must be removed - TOXIC this is the rule of both the liver and the kidneys. 

1. Blood circulates to the liver and the amino acid is broken down into molecules called the Urea. 
2. It then circulates to both of the kidneys. 
3. The kidneys will then filter the Urea from the bottom and the Urea will be added with water to form Urine. 
4. Urine will drain down the orators to collect down in the bladder.
5. Urea is now in the bladder in the form of Urine - it is removed from the body.
6. The filtered blood returns to the circulation with the toxic amino acids and urea removed. 

This is an example of excretion.  

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