The kidneys are dark red bean-shaped organs. Each kidney is enclosed in transparent membrane called the renal capsule which helps protect them against trauma and infection.

The kidney is divided into two main areas, the outer area is called the renal cortex and the inner area is called the renal medulla. Within the medulla there are 8 or more cone-shaped sections known as renal pyramids. The areas between the pyramids are called renal columns.

The kidneys are regulatory organs which filter the blood to remove waste products, salts and water which are then secreted from the kidneys as urine.

The main functional unit of the kidney is the nephron, and there are over a million nephrons in each kidney.