Tubular reabsorption

Tubular Reabsorption is a crucial process in the kidney that ensures the body retains essential substances from the urine before it is excreted. This process occurs in the renal tubule of the nephron, the functional unit of the kidney.

Overview

During urine formation, the kidneys filter out waste products and excess substances from the blood. However, this filtration process also includes essential substances such as glucose, amino acids, and electrolytes. Tubular reabsorption is the process by which these essential substances are reabsorbed back into the blood.

Mechanism

Tubular reabsorption primarily occurs in the proximal convoluted tubule, but also takes place in the loop of Henle, distal convoluted tubule, and collecting duct. The process involves both passive and active transport mechanisms.

Passive Reabsorption

Passive reabsorption occurs due to the concentration gradient created by the active reabsorption of substances. Water and some solutes are reabsorbed passively through the process of osmosis and diffusion.

Active Reabsorption

Active reabsorption involves the use of energy to transport substances against their concentration gradient. This is primarily how glucose and amino acids are reabsorbed.

Clinical Significance

Impaired tubular reabsorption can lead to various medical conditions. For instance, diabetes mellitus can cause an excess of glucose in the urine, a condition known as glycosuria, due to the inability of the renal tubules to reabsorb all the filtered glucose.

See Also

• Renal physiology
• Glomerular filtration
• Tubular secretion

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