The fine structure of gingival terminal vascular bed

Abstract

The fine structure of the different segments of the gingival terminal vascular bed has been studied. An electron microscopic investigation was undertaken of samples from the free gingiva of incisor and molar teeth of four rabbits. The different segments of the free gingival microvasculature were recognized as capillaries, postcapillary venules, muscular venules, and terminal arterioles. The capillary network of the free gingiva is structurally heterogeneous and consists of continuous and fenestrated capillaries, all with continuous basement membranes and scattered processes of pericytes. The fenestrated capillaries constitute about 30% of the total capillaries, and 97% of them are of the venous limb type, containing one or two fenestrae in a cross section. No apparent difference is noted between the number of fenestrated capillaries facing the crevicular and masticatory epithelia. The postcapillary venules have a larger vascular diameter than capillaries and an increased number of pericytes, which form an almost continuous layer. The smooth muscle cells are arranged around the endothelial tubes in the muscular venules and overlap each other. In the terminal arterioles, they form a continuous layer with well-developed cell contacts. The interendothelial junction in the different segments is characterized by adhesion belts with increased density of the subjacent cytoplasm. Surface modifications of the endothelial cells include marginal folds, plasmalemmal vesicles, and a variety of cellular projections into the surrounding connective tissue.