The aorta is a large blood vessel that branches off from the heart and pumps oxygen-rich blood back into the body. The aorta carries blood away from the left ventricle and circulates it into the systemic circuit. The systemic circuit are the vessels between the aortic semilunar valve and the entrance to the right atrium.
Oxygenated blood enters the body through capillary networks surrounding the alveoli of the lungs. Alveoli, air-filled pockets with barriers thin enough to allow oxygen to pass through, oxygenate the blood depleted of oxygen and absorb carbon dioxide for expulsion through the lungs. An exchange occurs at the alveoli, which transfers fresh oxygen from the lungs to the blood and carbon dioxide from the blood to the alveoli. The function of the aorta is to pump this new oxygen-rich blood from the left ventricle of the heart, where the oxygenated blood is deposited, and circulate it back into the body.
The shape of the aorta assists with blood circulation. It has four main sections: the ascending aorta, the aortic arch, the descending thoracic aorta and the abdominal aorta. The ascending aorta begins at the semilunar valve of the left ventricle and connects to the coronary arteries. The aortic arch curves like a cane and connects the ascending aorta and descending aorta. The descending aorta is a continuation of the aortic arch and is divided into the two sections: the thoracic aorta and the abdominal aorta.