Arteries: Arteries are vessels that convey blood away from the heart. The pulmonary arteries carry deoxygenated blood from the heart to the lungs; all other arteries carry oxygenated blood from the heart to all other parts of the body. Arteries and veins have walls composed of three layers: 1. Tunica intima: composed of a single layer of endothelial cells 2. Tunica media: made of smooth muscle 3. Tunica adventitia: composed of white fibrous connective tissue In the arteries, these three coats or tunics surround a hollow core known as a lumen though which blood flows. Arteries are thicker and stronger than veins with two major properties: elasticity and contractility.