How Kidneys Work

How Kidneys Work
Many people are surprised at how much the kidneys do and their importance to the body. Kidneys are filters that remove unwanted substances and excess fluid from the body. They also help make red blood cells, regulate blood pressure and maintain strong bones to name a few. When kidneys fail, patients can lose some or all of these important functions.

The kidneys lie near the middle of the back and are protected by the lower part of the rib cage. Each kidney is bean-shaped and about the size of your fist.

Kidneys act as a filtering system to get rid of excess water and wastes in the blood. Each kidney is made up of about one million tiny units called nephrons (NEF-rons). Inside each nephron is a filter, called a glomerulus (glo-MER-a-lus) and a complex array of tubes, called tubules (too-byools). Every day, about 800 cups of blood containing wastes pass through the kidneys. About 8 cups of excess water and waste get filtered out to the bladder as urine. The clean blood then goes back into the bloodstream.

For More Information:

Healthy Kidneys: What they do

What else do the kidneys do?

The kidneys also play a role in:

  • Making new red blood cells by producing the hormone erythropoietin (e-RITH-ro-POI-e-tin) which stimulates stem cells in the bone marrow.
  • Helping to control blood pressure by releasing the enzyme rennin (REH-nin).
  • Helping maintain strong bones and teeth by changing vitamin D into its active form which helps with the absorption of calcium from the intestine.