An artery is a blood vessel which carries blood away from the heart. It is the largest of all types of blood vessel, with strong vascular walls, the strength of which is required to move blood to body tissues which require oxygen.
The outer layer of an artery is called the tunica adventitia, which comes into contact with surrounding organs in order to protect the artery from wear. The inner layer is called a tunica intima has a smooth epithelium so that friction is reduced which is caused by blood flowing through the artery. The tunica media is the thickest layer and contains smooth muscle for contraction, to allow blood to flow through the artery .In the heart, there are two main arteries; the pulmonary artery and the aorta. The pulmonary artery carries deoxygenated blood to the lungs to become oxygenated (using haemoglobin) to bind oxygen.