Reabsorption

Reabsorption is a biological process that occurs in the kidney where the nephron filters out substances from the blood and then reabsorbs what the body needs back into the bloodstream. This process is crucial for maintaining the body's chemical balance.

Overview

Reabsorption primarily occurs in the proximal tubule of the nephron. Here, substances such as glucose, amino acids, and sodium are reabsorbed back into the bloodstream. This process is regulated by various hormones, including aldosterone and antidiuretic hormone (ADH).

Process

The process of reabsorption begins when the glomerulus filters the blood, creating a filtrate that enters the proximal tubule. Here, the cells lining the tubule actively transport substances such as glucose and amino acids back into the bloodstream. Sodium is also reabsorbed through passive transport.

Water reabsorption is influenced by the concentration of solutes in the filtrate and the permeability of the tubule. ADH increases the permeability of the tubule, allowing more water to be reabsorbed.

Regulation

The body regulates reabsorption to maintain homeostasis. For example, if the body is dehydrated, ADH levels increase to promote water reabsorption. Conversely, if the body has excess water, ADH levels decrease, reducing water reabsorption.

Aldosterone also plays a role in regulating reabsorption. It increases the reabsorption of sodium and water, which in turn increases blood volume and pressure.

Clinical significance

Abnormalities in reabsorption can lead to various health problems. For example, diabetes mellitus can cause excess glucose in the urine, a condition known as glycosuria. This occurs when the glucose concentration in the filtrate exceeds the reabsorption capacity of the proximal tubule.

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