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.
More Answers. The tunica externa, also known as the tunica adventitia, is the outermost layer of a blood vessel, surrounding the tunica media. It is mainly composed of collagen and is supported by external elastic lamina.The collagen serves to anchor the blood vessel to nearby organs, giving it stability.unica externa or tunica adventitia is the outer most layer of the blood vessels. It is mostly composed of collagen which helps to anchor the blood vessel with nearly organ. The second or middle layer of blood vessel is tunica media.