The Kidneys

There are two kidneys in the body, and they are situated on either side of the vertebral column between the thick muscles of the back and abdomen. Each kidney is approximately 10 cm long, 6 cm wide, and 4 cm thick. Each weighs about 140 gm.

The major function of the kidneys is to remove waste products from the body by producing urine. They contain about one million microscopic units called nephrons. Their function is to received and filters all the blood in the body. Once every twelve minutes they remove waste materials from the blood and return useful substances to the circulation. In the way, they enable the blood pressure remain constant.

The process of filtering the blood is as follows: first of all, blood enters the kidney from the renal artery and flows into the glomerulus, small knots of capillaries which act as filter. Fluid the passes into Bowman’s capsule, but the filter does not allow blood cells and large protein molecules to enter the capsule.

As the filtered fluid asses on, 80% of the water and sodium salt in it are removed and returned to the blood. The remaining liquid passes into collecting ducts, where water is again removed. The concentrated urine enters the renal pelvis and finally enters the bladder.