What are the different layers of the blood vessel walls called?

Answer 1

1.Tunica intima (Latin for innermost coat) is the innermost layer. Includes the endothelial lining and an underlying layer of connective tissue with a variable number of elastic fibers. In arteries the outer margin of the tunica intima cointains a thick layer of elastic fibers called the internal elastic membrane.

2.Tunica media (Latin for middle coat) is the middle layer. Contains concentric sheets of smooth muscle tissue in a framework of loose connective tissue. The collagen fibers bind the tunica media to the tunica intima and tunica externa. Commonly the thickest layer in the wall of a small artery, the tunica media es separated from the surrounding tunica externa by a thin band of elastic fibers called external elastic membrane. The smooth muscle cells of the tunica media encircle the endothelium linning the lumen of the blood vessel. When these smooth muscles contract, the vessel decreases in diameter; when they relax, the diameter increases. Large arteries also contain layers of longitudinally arrranged smooth muscle cells.

3.Tunica externa (Latin for outside coat) or tunica adventitia (Latin for coat that comes first) is theoutermost layer. Forms a connective tissue sheath. In arteries, this layer contains collagen fibers with scattered bands of elastic fibers. In veins, it is generally thicker than the tunica media and contains networks of elastic fibers and bundles of smooth muscle cells. The connective tissue fibers of the tunica externa typically blend into those of adjacent tissues, stabilizing and anchoring the blood vessel.