Answer: Connective tissue of the tunica media and endothelium of the tunica external
Explanation:
Blood vessels consists of networks that carry blood from the heart to the body cells and back to the heart. It comprises of veins and arteries.
Veins and arteries are made up of three layers and they are tunica intima,tunica media and tunica externa.
The innermost layer is tunica intima, the middle layer is tunica media and the outer layer is tunica externa.
Tunica media contain circular elastic fibers, connective tissues and smooth muscle.
The connective tissue serve as autoregulation of blood, that it help to maintain blood flow.
Tunica externa is the outermost layer that surrond tunica media, it also help to maintain blood flow through the blood vessels.
