1. How much blood do the kidneys clean everyday?

24 pints. Of this about 1.5 litre of urine is excreted from the body. This way, the kidneys help filter waste and unwanted materials from the blood and return the usable products back into the circulatory system

2. What is the main function of blood circulation?

The blood circulates oxygen to all the tissues in the body. Upon its return to the lungs, it brings carbon dioxide from the tissues to be exhaled from the lungs through the nose.