Gray448.png

Transverse section through a small artery and vein of the mucous membrane of the epiglottis of a child. X 350. (Klein and Noble Smith.) A. Artery, showing the nucleated endothelium, e, which lines it; the vessel being contracted, the endothelial cells appear very thick. Underneath the endothelium is the wavy elastic lamina. The chief part of the wall of the vessel is occupied by the circular muscle coat m; the rod-shaped nuclei of the muscle cells are well seen. Outside this is a, part of the adventitia. This is composed of bundles of connective tissue fibers, shown in section, with the nuclei of the connective tissue corpuscles. The adventitia gradually merges into the surrounding connective tissue. V. Vein showing a thin endothelial membrane, e, raised accidentally from the intima, which on account of its delicacy is seen as a mere line on the media m. This latter is composed of a few circular unstriped muscle cells a. The adventitia, similar in structure to that of an artery.