how does the kidney filters blood?

Answer 1

5 litres, on average

Answer 2

The kidney filters by passing high pressure blood through a series of narrower blood vessels in a glomerulus. There are many of these inside a kidney. The action of high blood pressure going into a narrow tube effectively pushes the fluid against the vessel walls, filtering a lot of substances out of the kidneys and into the fluid known as the filtrate. A lot of this is resorbed back into the blood in the Loop of Henle, as the kidneys filter 100ml of fluid a minute. 95% of this is resorbed.