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.
Best Answer: The upper layer of the slin is called the 'epidermis'. It contains no blood vessels or nerves. Blood nourishes this layer by diffusion.The middle layer of the skin, the layer that is asked about in this question is called the 'dermis' and conatins blood vessels, nerves and other structures. The lower layer of the skin is called the 'sub-cutis' and contains fat.est Answer: The upper layer of the slin is called the 'epidermis'. It contains no blood vessels or nerves. Blood nourishes this layer by diffusion.