Which tunic is the middle coat of a blood vessel?

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

Answer: (C)

The middle coat of a blood vessel is the tunica media. This layer is made up mainly of smooth muscle (with some elastic fibers), which lets the vessel constrict or dilate to regulate blood flow and blood pressure. The inner lining, tunica intima, faces the lumen and includes endothelium, while the outer layer, tunica externa (adventitia), is a connective tissue sheath that anchors the vessel to surrounding tissues. The tunica media’s muscular composition is what defines it as the middle coat.