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.
They are tiny branches of arteries that lead to capillaries and help maintain the pressure and blood flow in the body. Venous valves prevent blood from flowing in the opposite direction. Connective tissues make up the outermost layer of a vein which is also known as-tunica adventitia or tunica externa.rteries that carry blood from the heart to other parts of the body are known as systemic arteries while those that carry deoxygenated blood to the lungs are known as pulmonary arteries.