Which layer is the innermost layer of arteries?

Which layer is the innermost layer of arteries?

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

Answer: (B)

The innermost layer of arteries is the tunica intima. This lining sits directly next to the blood in the vessel lumen and is made up principally of endothelial cells. In larger arteries, the intima also includes a thin subendothelial connective tissue layer and sometimes an internal elastic lamina. The tunica media lies outside of it and contains smooth muscle and elastic fibers, while the tunica externa (adventitia) is the outer connective tissue layer. While endothelium refers to the endothelial cell lining, it is part of the tunica intima, not a separate inner layer.

The innermost layer of arteries is the tunica intima. This lining sits directly next to the blood in the vessel lumen and is made up principally of endothelial cells. In larger arteries, the intima also includes a thin subendothelial connective tissue layer and sometimes an internal elastic lamina. The tunica media lies outside of it and contains smooth muscle and elastic fibers, while the tunica externa (adventitia) is the outer connective tissue layer. While endothelium refers to the endothelial cell lining, it is part of the tunica intima, not a separate inner layer.