The kidneys are two bean-shaped organs, each about the size of a fist. They
are located just below the rib cage, one on each side of the spine. Every day,
the two kidneys filter about 120 to 150 quarts of blood to produce about 1 to 2
quarts of urine, composed of wastes and extra fluid. The urine flows from the
kidneys to the bladder through two thin tubes of muscle called ureters, one on
each side of the bladder. The bladder stores urine. The muscles of the bladder
wall remain relaxed while the bladder fills with urine. As the bladder fills to
capacity, signals sent to the brain tell a person to find a toilet soon. When
the bladder empties, urine flows out of the body through a tube called the
urethra, located at the bottom of the bladder. In men the urethra is long, while
in women it is short.
Healthy kidneys handle several specific roles. Healthy kidneys:
Maintain a balance of water and concentration of minerals, such as
sodium,potassium, and phosphorus, in your blood
Remove waste by-products from the blood after digestion, muscle activity, and
exposure to chemicals or medications
Produce renin, an enzyme that helps regulate blood pressure
Produce erythropoietin, which stimulates red blood cell production
Produce an active form of vitamin D, needed for bone health
