Vein cells called tunica intima. The precise location of veins varies much more from person to person than that of arteries. Veins serve to return blood from organs to the heart. Veins are also called "capacitance vessels" because most of the blood volume (60%) is contained within veins. In systemic circulation oxygenated blood is pumped by the left ventricle through the arteries to the muscles and organs of the body, where its nutrients and gases are exchanged at capillaries. After taking up cellular waste and carbon dioxide in capillaries, blood is channeled through vessels that converge with one another to form
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