Kapillaariseinän

Kapillaariseinän refers to the wall of a capillary, which are the smallest blood vessels in the body. These vessels form a crucial part of the circulatory system, connecting arterioles and venules. The wall of a capillary is extremely thin, typically only one cell layer thick. This single layer is composed of endothelial cells.

The thinness of the capillary wall is essential for its primary function: the exchange of substances between the blood and the surrounding tissues. Oxygen, nutrients, hormones, and other vital molecules can easily diffuse from the blood into the interstitial fluid, and subsequently into the cells. Conversely, waste products such as carbon dioxide and urea move from the tissues back into the blood.

The endothelial cells forming the capillary wall are supported by a basement membrane, which is a thin layer of extracellular matrix. This membrane provides structural support and also plays a role in regulating the passage of molecules. While most capillaries are continuous, meaning their endothelial cells form an unbroken sheet, there are also fenestrated capillaries that have pores or openings, allowing for more rapid transport of certain substances. These are found in organs where filtration or absorption is a major function, such as the kidneys and the small intestine. The structure of the kapillaariseinän is thus perfectly adapted to facilitate efficient and selective exchange within the microcirculation.