Which layer of blood vessels contains smooth muscle?

A) tunica externa
B) tunica media
C) tunica intima
D) none of the above

Tunica Media

The middle, muscular layer of the walls of arteries and veins, responsible for regulating the diameter of the vessels.

Smooth Muscle

A type of muscle found in the walls of internal organs such as the intestines and blood vessels, responsible for involuntary movements.