What is the function of the Kidneys?
The main functions of the kidney in order of importance are:
- blood pressure control
- salt and water balance
- erythropoietin (a hormone) production
- vitamin D metabolism
The kidneys secrete hormones:
- renin (instrumental in controlling blood pressure)
- erythropoeitin (which helps control the production of red blood cells)
They filter the blood to get rid of excess fluid, waste products, many drugs and regulate the composition of body fluids and salts.
They are essential for Vitamin D metabolism (with the result of stimulating the absorption of calcium and phosphorus from the small intestine, and keeping it in balance).
The kidneys are two organs which lie in the back of the abdominal cavity. They are around four to five inches long, and they have several functions.
The blood supply to the kidneys comes from the renal arteries, which branch off the aorta. The kidneys have a very considerable blood supply, (25% of the total cardiac output, or 1300 millilitres of blood pass through the kidneys per minute).
Each kidney has around one million nephrons, which are microscopic units which filter the blood (removing wastes and extra water) and which produce urine. A person, who normally has two kidneys will have two million nephrons.
A person can live a healthy life with one healthy kidney as it can cope with all the necessary functions.
The filtration of blood produces urine. The urine is then collected in the ureters, which are long muscular tubes which act as conduits, taking the urine produced by the kidneys to the bladder. Urine is stored in the bladder, an expandable muscular organ, until it is full, until the need to urinate is signalled to the brain through the nervous system, and the bladder sphincter opens (as a voluntary action) to allow the urine to flow out through another tube called the urethra.
Click on the following link for details of:
- Common causes/problems affecting the kidneys
- Kidney Failure
- Diagrams of nephron and glomerulus
- Diagram of Urinary Tract
Amended April 2008