Arteriole. Light micrograph of a longitudinal section through an arteriole blood vessel (passing through the pancreas). Arterioles carry blood from the arteries to the network of capillaries that supply oxygen and nutrients to the body tissues. The arteriole possesses a thick, muscular wall which enables it to carry blood under pressure. The wall is mainly composed of smooth muscle fibers, which are found in the middle layer of the wall, the tunica media (purple). Magnification: 200x at 35mm