Kapillarpermeabilität

Kapillarpermeabilität refers to the property of blood vessel walls, specifically capillaries, that allows for the passage of substances between the blood and the surrounding tissues. Capillaries are the smallest blood vessels in the circulatory system and their thin walls, typically a single layer of endothelial cells, are crucial for this exchange. The permeability of capillaries is not uniform and can vary depending on the location and physiological state of the tissue.

Several factors influence capillary permeability. These include the size of the molecules being transported, the pressure gradients across the capillary wall, and the presence of specific transport mechanisms. Small lipid-soluble molecules can diffuse directly across the endothelial cell membranes. Water-soluble substances, however, often pass through intercellular clefts, fenestrations (pores in the endothelial cells), or via vesicular transport.

Increased capillary permeability can be a hallmark of inflammation. Inflammatory mediators, such as histamine and bradykinin, can cause the endothelial cells to contract or form gaps, widening the intercellular clefts and allowing more fluid, plasma proteins, and immune cells to leak into the interstitial space. This contributes to the classic signs of inflammation like swelling (edema) and redness. Conversely, conditions that reduce capillary permeability can impair nutrient and oxygen delivery to tissues and hinder waste removal. Understanding capillary permeability is fundamental to comprehending physiological processes like nutrient absorption, waste excretion, and the inflammatory response.