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.
Inside this layer is the tunica media, or media, which is made up of smooth muscle cells and elastic tissue. The innermost layer, which is in direct contact with the flow of blood is the tunica intima.This layer is made up of mainly endothelial cells.eins: The thick, outer-most layer of a vein is made of collagen, wrapped in bands of smooth muscle while the interior is lined with epithelial cells called intima. Most veins have one-way flaps called venous valves that prevent blood from flowing back and pooling in the lower extremities due to the effects of gravity.