The kidneys are a pair of organs on either side of the spine in the lower abdomen. Each kidney is about the size of a fist. Attached to the top of each kidney is an adrenal gland. A mass of fatty tissue and an outer layer of fibrous tissue (Gerota's fascia) enclose the kidneys and adrenal glands.

This picture shows the kidney and adrenal gland.

The kidneys are part of the urinary tract. They make urine by removing wastes and extra water from the blood. Urine collects in a hollow space (renal pelvis) in the middle of each kidney. It passes from the renal pelvis into the bladder through a tube called a ureter. Urine leaves the body through another tube (the urethra).

The kidneys also make substances that help control blood pressure and the production of red blood cells.

This picture shows the male urinary tract.

This picture shows the female urinary tract.

Glossary Terms

The area of the body that contains the pancreas, stomach, intestines, liver, gallbladder, and other organs.

A small gland that makes steroid hormones, adrenaline, and noradrenaline. These hormones help control heart rate, blood pressure, and other important body functions. There are two adrenal glands, one on top of each kidney. Also called suprarenal gland.

The organ that stores urine.

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.

Containing or resembling fibers.

One of a pair of organs in the abdomen. Kidneys remove waste from the blood (as urine), produce erythropoietin (a substance that stimulates red blood cell production), and play a role in blood pressure regulation.

A part of the body that performs a specific function. For example, the heart is an organ.

A cell that carries oxygen to all parts of the body. Also called erythrocyte and RBC.

The area at the center of the kidney. Urine collects here and is funneled into the ureter, the tube that connects the kidney to the bladder.

A group or layer of cells that work together to perform a specific function.

The tube that carries urine from the kidney to the bladder.

The tube through which urine leaves the body. It empties urine from the bladder.

The organs of the body that produce and discharge urine. These include the kidneys, ureters, bladder, and urethra.

Fluid containing water and waste products. Urine is made by the kidneys, stored in the bladder, and leaves the body through the urethra.