Blood vessel is a tubular structure. Luminal surface of the vessel wall is lined by endothelium. A vessel that carries blood away from heart is an artery. Lumen of an artery is patent. Blood flows through an artery with pressure. A vessel that carries blood towards heart is a vein. Lumen of a vein is collapsed. Blood flows through a vein with less pressure than in the artery. This chapter covers the large artery or elastic artery or conducting artery or resilient artery, medium-sized artery or muscular artery or distributing artery or resistance artery, and large vein. Large vein has thin vessel wall than artery. Vessel wall has three layers tunica intima, tunica media, and tunica adventitia.