Muscular artery. Light micrograph of a transverse section through the wall of a muscular artery,showing its structure. This vessel carries blood under high pressure. Its thick wall is composed of three layers. The innermost tunica intima surrounds the lumen (tube,white). It possesses a fine elastic sheet (convoluted,bottom left) known as the internal elastic lamina. The middle layer,the thick tunica media,is mainly composed of smooth muscle fibres (purple),interspersed with a few connective collagen fibres (blue). The external tunica adventitia (blue) is composed mainly of connective tissue. Trichrome blue stain. Magnification unknown |