The integrity of uterine circulation is essential for normal pregnancy outcome. The present study describes for the first time the histology, histochemistry, and ultrastructure of the different types of vessels in the uterus at critical early stages of pregnancy. Arteries were congested and showed PAS-positive granules. veins characterized by its wide lumen and thick adventitia rich in collagen and elastic fibers and showed PAS-positive reaction in their wall. Lymphatics showed a positive reaction with PAS-AB combination. Many arteriols observed in the uterine wall and showed PAS-positive granules and venules appeared congested in the endometrium. Spiral artery and arterial sinuses also demonstrated. Anastomosis between arterioles and venules was recorded. Blood vessels of a special structure were demonstrated presenting a vascular wall of variable thickness, unevenly distributed smooth muscle in the wall, smooth muscle fibers arranged in a different direction. Spirally oriented arterioles and venules were also demonstrated. Sclerotic changes observed in the wall of some vessels. Glomus cells observed in the wall of many arteries, arterioles, spirally oriented arterioles, and arteriovenous anastomosis. filopodia-like protrusions and caveolae were the most characteristic feature of the endothelium.
