The body takes nutrients from food and converts them to energy. After the body has used all the food components that it needs, waste products are left behind in the bowel and in the blood.
The kidneys and urinary system help
to excrete the waste products. They also keep chemicals, such as potassium and sodium,
and water in balance. Kidneys filter and remove several toxic materials from the body
that are the products of food metabolism. These waste materials can cause problems in
the body if they build up. The kidneys also control the fluid and acid-base balance in
The kidneys are 2 bean-shaped
organs. They are located below the ribs toward the middle of the back. Their function is
Remove liquid waste from the blood in the form of urine
Keep a stable balance of
chemicals, such as salts and other substances in the blood
The kidneys remove waste products
called urea from the blood through nephrons. Nephrons are tiny filtering units. There
are about one million nephrons in each kidney. Each nephron consists of a ball formed of
small blood capillaries, called a glomerulus, and a small tube called a renal tubule.
Blood enters the glomerulus and is filtered there. This filtered fluid then passes
through the tubule where substances and water are added or removed. The fluid that
remains is urine.
Once the urine is formed, it passes through the nephrons and down the renal tubules of the kidney. Urine collects in the calyces and renal pelvis and moves into the ureter. From here it flows down into the bladder.
Along with filtering waste from the
blood and helping in the balance of fluids and other substances in the body, the kidneys
do other vital functions. The kidneys:
Release hormones, such as renin, that help to regulate blood pressure
Make erythropoietin, a
hormone that aids formation of red blood cells
Convert vitamin D into a form that can be used by the body's tissues
Interact with corticosteroids
(made by the adrenal glands that sit on top of each kidney) that help to regulate
kidney function and the body’s inflammatory response system