The Kidneys: Structure and Function
By: David Mangusan Jr., PTRP
The two kidneys are bean-shaped organs located near the middle of the back, just below the rib cage or just above the waist to the left and right of the vertebral column (spine). Each kidney is about the size of a tightly clenched fist, these organs act as sophisticated filters for the body. They process about 200 quarts of blood a day to sift out about 1 - 2 quarts of waste products and extra water that eventually leave the body as urine.
Here are some of the major functions of the kidneys:
- The kidneys are the major excretory organs of the body. They remove waste products from the blood.
- The kidneys help to regulate the concentration of ions, such: as sodium, calcium, potassium and phosphate ions, in body fluids.
- The kidneys play a very important role in regulating blood volume by regulating the volume of water removed from the blood.
- The kidneys also help in regulating the pH of body fluids.
- Along with the skin and the liver, the kidneys also participate in the formation of vitamin D. Vitamin D is important for the absorption of calcium by the intestine.
.gif)
.gif)
Blood enters the kidneys through arteries that branch inside the kidneys into tiny clusters of looping blood vessels. Each cluster is called a glomerulus (Greek word meaning filter).
There are approximately 1 million glomeruli (plural form of glomerulus) in each kidney. The glomerulus is attached to the opening of a small fluid-collecting tube called the renal tubule. Blood is filtered in the glomerulus, and extra water and wastes pass into the renal tubule and become urine. Eventually, the urine drains from the kidneys into the urinary bladder through larger tubes called ureters.
Each glomerulus-and- renal tubule unit is called a nephron. Nephrons are the functional units of the kidneys. Each kidney is composed of about 1 million nephrons. In healthy nephrons, the glomerular membrane (glomerular or Bowman’s Capsule) that separates the blood vessel from the tubule allows waste products and extra water to pass into the tubule while keeping blood cells and protein in the bloodstream.
