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.
1 Arteries. 2  Arteries are elastic vessels that transport blood away from the heart. 3  Pulmonary arteries carry blood from the heart to the lungs where oxygen is picked up by red blood cells. 4  Systemic arteries deliver blood to the rest of the body.5  Veins. 6  Veins are elastic vessels that transport blood to the heart.he inner blood vessel layer is formed of endothelium. In capillaries and sinusoids, endothelium comprises the majority of the vessel. Blood vessel endothelium is continuous with the inner tissue lining of organs such as the brain, lungs, skin, and heart. In the heart, this inner layer is called the endocardium.