the disk in the fundus of the eye marking the point at which the optic nerve enters; it is accompanied by blood vessels, is oval, light in color and the blind spot of the retina.
ARTERIOLES. In arterioles, the tunica intima consists of a continuous endothelium and a very thin subendothelial layer. In addition, a thin, fenestrated internal elastic lamina is present in larger arterioles but absent in terminal arterioles. Generally, the tunica media consists of 2 layers of smooth muscle cells.
Smooth muscle is found within the walls of blood vessels (such smooth muscle specifically being termed vascular smooth muscle) such as in the tunica media layer of large (aorta) and small arteries, arterioles and veins. Also, smooth muscle may contain MHC that is not involved in contraction, and that can arise from multiple genes. 2  Myosin II also contains 4 light chains, resulting in 2 per head, weighing 20 (MLC 20) and 17 (MLC 17) kDa. 3  These bind the heavy chains in the neck region between the head and tail.