1. Comparison of the three major layers or tunics in the largest artery and vein. (a) Aorta, (b) vena cava. Simple squamous endothelial cells (arrows) line the intima (I) that has subendothelial loose connective tissue and is separated from the media by the internal elastic lamina (IEL), a sheet of elastin. The media (M) contains many elastic lamellae and elastic fibers (EF) alternating with layers of smooth muscle. The media is much thicker in large arteries than veins, with relatively more elastin. Elastic fibers are also present in the outer tunica adventitia (A), which is relatively thicker in large veins. Vasa vasorum (V) are seen in the adventitia of the aorta. The connective tissue of the adventitia always merges with the less dense connective tissue around it. Both X122. Elastic stain.
Source: Chapter 11. The Circulatory System, Junqueira’s Basic Histology, 13e
Citation: Mescher AL. Junqueira’s Basic Histology, 13e; 2013 Available at: Accessed: October 01, 2017
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