Kidneys

Anatomy of the Kidneys

The kidneys are a pair of bean-shaped, brown organs about the size of your fist. These organs are located in the superior lumbar region of the body.

The kidneys continuously clean the blood and adjust the composition of the blood including the amounts of water, electrolytes, and pH. These hard-working organs must have a very rich blood supply in order to accomplish this. The kidneys receive between 1,100-2,200 L of blood per day (about the volume of a car). This means that all of your blood runs through the kidneys to be cleaned about once every four minutes. Blood is carried to the kidneys through the renal artery and is carried from the kidneys by the renal vein.

Due to the function of the kidneys, it is necessary for them to be allowed a large supply of blood. This is why blood vessels connect them to the main arteries and veins that run directly to and from the heart. Because the kidney contains so much blood, bleeding is a major hazard when it gets injured. To avoid physical damage, each kidney is covered by a tough capsule of connective tissue called the renal capsule, and embedded in two layers of fatty tissue acting as a shock absorber. Both kidneys are also protected from the outside world by strong muscles and ribs at the back and the abdomen with its muscle at the front. Kidney anatomy

See description of diagram

There are three major regions of the kidney:

cortex - outer region
medulla - inside the cortex
pelvis - inner collecting tube (blood vessels and ureters)

The structural and functional unit of the kidney is the nephron. The nephron is the actual structure that removes waste from the blood. A single kidney may have more than a million nephrons!

Function of Kidneys

The kidneys are powerful chemical factories that perform the following functions:

remove waste products from the body
remove drugs from the body
balance the body's fluids
release hormones that regulate blood pressure
produce an active form of vitamin D that promotes strong, healthy bones
control the production of urine

Most people know that a major function of the kidneys is to remove waste products and excess fluid from the body. These waste products and excess fluid are removed through the urine. Urine is the liquid waste product of the body that is excreted by the urinary system. The production of urine involves highly complex steps of excretion and reabsorption. This process is necessary to maintain a stable balance of body chemicals.

The kidneys have many other important homeostatic functions in the body. They perform the critical regulation of the body's salt, potassium and acid content. These organs also produce hormones that affect the function of other organs. For example, a hormone produced by the kidneys stimulates red blood cell production. Other hormones produced by the kidneys help regulate blood pressure and control calcium metabolism. The regulation of water levels is another very important function of the kidneys. If the blood becomes too dilute or too concentrated with solutes, then it can interfere with normal cellular activity. The kidneys are able to regulate water concentration in the blood by removing excess water if the blood is too dilute or conserving water in the blood if it is not dilute enough.

By regulating solute numbers and water volume, the kidneys normally maintain homeostasis in blood solute concentration.

Factors that Affect Kidney Function
Factors That Affect Kidney Function
Antidiuretic Hormone (ADH)	Prevents excess water loss from kidneys.
Alcohol	Inhibits secretion of ADH; this results in a higher urine volume.
Aldosterone	Prevents excess loss of sodium and water from kidneys.
Caffeine	Increases rate of salt and water loss from kidneys.
Increased Blood Pressure	Increase rate of water loss from kidneys.

Review kidney function and anatomy by watching the video and completing the learning object below.

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