Gefäßschichten

Gefäßschichten, also known as vessel layers or tunics, refer to the distinct layers that form the wall of blood vessels. These layers are crucial for the structural integrity and functional capabilities of arteries, veins, and capillaries.

The outermost layer is the tunica adventitia, also called the tunica externa. This connective tissue layer provides support and anchors the vessel to surrounding tissues. It is primarily composed of collagen and elastic fibers.

Beneath the tunica adventitia lies the tunica media, the middle layer. This layer is the thickest in arteries and is composed mainly of smooth muscle and elastic fibers. The smooth muscle allows for vasoconstriction and vasodilation, regulating blood pressure and flow. The elasticity of the tunica media is vital for withstanding the pulsatile pressure from the heart in arteries. In veins, the tunica media is thinner and contains less smooth muscle and elastic tissue.

The innermost layer is the tunica intima, also known as the endothelium. This is a single layer of flattened endothelial cells that lines the lumen of the vessel. It provides a smooth surface for blood flow, preventing clot formation and facilitating nutrient and waste exchange. In arteries, the tunica intima also contains a layer of elastic tissue called the internal elastic lamina.

Capillaries, the smallest blood vessels, consist only of a single layer of endothelial cells, a basement membrane, and a thin layer of connective tissue, lacking the distinct tunica adventitia and tunica media found in larger vessels. This simple structure facilitates efficient diffusion of substances between blood and tissues. The specific composition and thickness of these layers vary depending on the type of blood vessel and its location in the circulatory system.