Excretory System

What are Kidneys

Kidneys are a pair of organs responsible for filtering wastes and excess water from the BLOOD, excreting both from the body as URINE. The kidneys maintain the body’s fluid and electrolyte balances, and also produce hormones that regulate the production of new erythrocytes (ERYTHROPOIETIN [EPO]) and BLOOD PRESSURE (RENIN). With each heartbeat about 20 percent of the body’s blood supply surges through the kidneys. The body’s entire blood supply passes through the kidneys about two dozen times a day. Though the kidneys are essential for life, a single functioning kidney can adequately sustain life in most people. The kidneys are fully functional from birth.

Function
The pressure of the blood as it flows through the glomeruli helps force molecules of water and other substances across the membranous glomerular walls and into an encapsulated structure called Bowman’s capsule. Specialized proteins called transporters carry these substances across the capillary membranes. …