The aorta is the major blood vessel of the human body. It is an artery which carries oxygenated blood from the heart to the rest of the body. The walls of the aorta are composed of three layers of connective tissue and elastic fibers. These layers are the tunica adventitia, the tunica media, and the tunica intima. Being a long continuous tube, the aorta artery is divided into three sections: 1) the ascending aorta, which is the first section that arises from the left ventricle of the heart and then goes upward; 2) the aortic arch, which is the middle section that forms an inverted U or arch, giving off the brachiocephalic artery, left common carotid artery, and the left subclavian artery; 3) the descending aorta, the third section which extends down to the abdomen, where it branches off into the iliac arteries.
In the chest, several paired branches shoot off from the aorta: bronchial arteries, mediastinal arteries, esophageal arteries, pericardial arteries, and superior phrenic arteries. In the abdomen, the aorta gives off smaller arteries that supplies the organs of the abdominal cavity: the celiac artery, the superior mesenteric artery, and inferior mesenteric artery. Then, the aorta keeps runnng down the abdomen until it finally branches off into the iliac arteries that go down to the legs.