Most people have two kidneys. They sit at the back of the body, one on each side, just underneath the ribcage. The kidneys filter the blood and remove waste products, which they convert into urine.
Urine drains from each kidney, through a tube called a ureter, to the bladder where it is stored. When you're ready to pass urine it leaves the body through another tube called the urethra.
Blood is carried to the kidney through a blood vessel called the renal artery. Renal means ‘to do with the kidney’. After the blood has been filtered by thousands of tiny filters called nephrons, it travels back to the rest of the body through the renal vein.
The kidneys also help to control the balance of fluid, salt and minerals in the body and to maintain blood pressure.
The kidneys are contained in a fibrous covering called the Gerota’s fascia and surrounded by a layer of fat. The outer part of the kidney that makes urine is called the cortex. The inner part that collects urine is called the medulla.
On top of each kidney sits a small gland called the adrenal gland, which produces important hormones.