important role is to regulate the movement of materials into and out of cells. The phospholipid bilayer structure (fluid mosaic model) with specific membrane. proteins accounts for the selective permeability of the membrane and passive. and active transport mechanisms.
Structure of Blood Vessels a) Three distinct layers or tunics form the walls of blood vessels: ---The tunica interna (tunica intima) is the innermost layer.It contains the endothelium which is a continuation of the endocardial lining of the heart.tructure of Blood Vessels a) Three distinct layers or tunics form the walls of blood vessels: ---The tunica interna (tunica intima) is the innermost layer.
Arteries and veins are composed of three tissue layers. The thick outermost layer of a vessel (tunica adventitia or tunica externa ) is made of connective tissue. The middle layer ( tunica media ) is thicker and contains more contractile tissue in arteries than in veins. It consists of circularly arranged elastic fibers, connective tissue, and smooth muscle cells. The inner layer ( tunica intima ) is the thinnest layer, comprised of a single layer of endothelium supported by a subendothelial layer.