Blood vessel between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart. The word "vascular", meaning relating to the blood vessels, is derived from the Latin "vas", meaning vessel. A few structures (such as cartilage and the lens of the eye) do not contain blood vessels and are labeled. The arteries and veins have three layers. The middle layer is thicker in the arteries than it is in the veins: Capillaries consist of little more than a layer of endothelium and occasional connective tissue. When blood vessels connect to form a region of
Endometrial arteries arteries are coiled and is why they are also called spiral arteries. The spiral arteries are coiled towards the upper part of the endometrium and straight towards the base of the endometrium. In the endometrium there are straight and serial arteries. Straight arteries specifically branch to the base of the endometrium therefore supplying blood to the base of the endometrium. Spiral arteries supply blood to the rest of the endometrium. They grow rapidly, covering much of the space of the endometrium and end up coiled. When hormones levels are low, the endometrial arteries react by becoming narrow. Endometrial arteries supply