NEPHRONS - The Kidneys' Filtration Unit
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Nephrons are microscopic tube-like structures in the kidneys that filter the
blood and cause wastes to be removed. They are the most basic structure of the
kidney's anatomy, and are an integral part of the
urinary system. Each kidney contains approximately one million of them.
While they may look like tangles of vessels and tubules, nephrons have an orderly structure, designed to perform the essential process of filtering the blood.
The Glomerulus is the primary structure of the filtering process. It regulates the concentration of essential substances such as potassium, calcium, and hydrogen, and removes substances not produced by the body such as drugs and food additives. The Glomerulus is contained inside a cup-shaped structure known as the Bowman's capsule, from which extends the Renal tubule. This tubule makes a number of turns and loops and eventually leads to the Collecting tubule. The part of the renal tubule that loops around into a 'U' turn is called the Loop of Henle. THE FILTERING PROCESS The substances extracted from the blood remain in the Bowman's Capsule... while the filtered blood moves along tiny vessels called Capillaries, and exits the kidney through the Renal Vein. Some of the substances that are removed from the blood are useful to the body while some are not. As these substances move along the renal tubule the useful substances, such as water, salt, amino acids and glucose are reabsorbed back into the blood stream through the Capillaries. The other substances that are not useful to the body, such as excess water and salt, urea, uric acid... continues to move along the renal tubule into the Collecting tubule. From the Collecting tubule the waste products go to the ureter then into the bladder... then eventually expelled from the body (as urine). In summary, nephrons are the central filtration system of the kidneys. They are responsible for filtering water, urea, salt, glucose, amino acids and other trace substances from the blood. Many of the filtered materials are then reabsorbed into the blood to be reused by the body, to maintain normal body functions. The waste materials remain behind to be excreted as waste products in the urine. These microscopic structures are not only responsible for keeping the body's chemistry clean, but they also help to ensure that the correct concentration of the blood is maintained.
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