What is capillary permeability?

Capillary permeability refers to the ability of small molecules and fluids to pass through the walls of capillaries, the smallest blood vessels in the body. The capillary walls are composed of endothelial cells that are held together by tight junctions. These junctions allow for the passage of small molecules such as oxygen, carbon dioxide, and glucose, while larger molecules such as proteins and blood cells are prevented from passing through.

Capillary permeability is regulated by a complex interplay of various biochemical and physiological factors, including inflammation, vascular pressure, and the actions of certain hormones. When there is inflammation or tissue damage, the capillary walls become more permeable to allow for the influx of immune cells and molecules that can help repair the affected tissue.

Abnormal increases in capillary permeability can lead to edema (swelling) in the affected tissue, while decreases in permeability can result in poor blood flow and decreased tissue oxygenation. Certain diseases and conditions such as sepsis, diabetes, and heart failure can cause alterations in capillary permeability. Drugs that affect capillary permeability, such as vasodilators and vasoconstrictors, are commonly used in the management of various medical conditions.