Question: What is the main funtion of a kidney?

Sean Murphy answered on 22 Mar 2012:

Kidneys act like a filter to make sure the right amount of wastes and fluids are removed. Every hour your blood supply circulates through the kidneys about 12 times. Each day your kidneys process around 200 litres of blood, with around 1 to 2 litres of waste leaving the body as urine. Our kidneys make three important hormones, erythropoietin, renin and active vitamin D. Erythropoietin stimulates the production of red blood cells, renin is involved in the control of blood pressure and active vitamin D controls calcium uptake and helps make strong bones.