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.
The tunica interna is the innermost lining of the blood vessel. It is lined by endothelium, which is almost always simple squamous epithelium, and its underlying connective tissue. In arteries a layer of elastic tissue called the internal elastic membrane marks the outer boundary of the tunica interna.2.. Continuous capillaries have an endothelial lining with the endothelial cells closely attached to one another by tight junctions and desmosomes. This type of capillary is the most common and most closely regulates exchange of materials.