The innermost layer of a blood vessel is the

The innermost layer of a blood vessel is the

• A. Lumen
• B. Tunica externa
• C. Tunica media
• D. Tunica intima

Answer: (D)

Blood vessels have three main layers, with the innermost lining facing the blood being the tunica intima. This layer is made primarily of endothelial cells that create a smooth surface to reduce friction, regulate permeability, and help control vessel tone. In larger vessels there can also be a subendothelial connective tissue layer and sometimes an internal elastic lamina just beneath the endothelium. The lumen is the hollow passage where blood flows, not a tissue layer. The middle layer is the tunica media, composed of smooth muscle that controls diameter, and the outer layer is the tunica externa (adventitia), which provides support and anchorage. So, the innermost layer is tunica intima.

Blood vessels have three main layers, with the innermost lining facing the blood being the tunica intima. This layer is made primarily of endothelial cells that create a smooth surface to reduce friction, regulate permeability, and help control vessel tone. In larger vessels there can also be a subendothelial connective tissue layer and sometimes an internal elastic lamina just beneath the endothelium. The lumen is the hollow passage where blood flows, not a tissue layer. The middle layer is the tunica media, composed of smooth muscle that controls diameter, and the outer layer is the tunica externa (adventitia), which provides support and anchorage. So, the innermost layer is tunica intima.