Vascular Histology (I): The coronary arteries.

A. Light micrograph of a coronary artery from a normal 30 year old individual. The intima is slightly thickened by muscular proliferation, but there is no evidence of foamy change in macrophages or smooth muscle cells. The internal and external elastic laminae are evident as black, slightly wavy structures. The media is thicker than the intima and the smooth muscle cells are oriented perpendicular to the longitudinal axis of the vessels. The adventitia is prominent and contains, thick wavy bundles of collagen (Movat pentachrome, 100X). B. In the newborn, the epicardial coronary arteries have the same architecture as in adults, but show a complete absence of intimal proliferation (Movat pentachrome, 50X). C. The coronary arteries are terminal arteries, with essentially no anastomoses between the branches of the major epicardial vessels in humans. This micrograph shows a small intramyocardial coronary artery and venule. Note the absence of a muscular wall in the venule. In contrast, the artery has a small, muscular media. The adventitia is usually prominent in intramyocardial coronary vessels, since this layer provides support to the vessel during pulsatile flow. D. Coronary veins show a thin media underlying the single layer of endothelial cells. The adventitia is looser and less structured than in arteries and allows for great distention of the lumen of the vessel. E. Ultrastructural examination of both arteries and veins normally shows well organized smooth muscle cells with numerous loosely organized actin filaments. These filaments are anchored to dense bodies (arrows) that are located subjacent to the plasma membrane. Intracellular organelles are sparse (8,000 X). F. Light micrograph of the epicardial surface of the left ventricle from an elderly patient showing dilated lymphatic vessels (arrows). {14} (Masson trichrome, 5X)

The following panel will show you the histology of the great vessels