The aorta is the largest blood vessel of the body. It is the main artery that supplies every organ and tissue through a complex network of arterial branches. All arteries constituting the greater systemic circulation emerge from the aorta, which arises from the aortic orifice in the left ventricle of heart. It is divided into the ascending aorta, the arch of the aorta, and the descending aorta. The descending aorta is subdivided in turn into the thoracic aorta and the abdominal aorta.
The ascending aorta originates from the aortic orifice as a continuation of the aortic vestibule of the left ventricle. Then it ascends obliquely to the right and front to be continuous with the arch of the aorta. At its origin, the ascending aorta is dilated; this is called the bulb of the aorta. The wall of this bulb forms three bulges called the sinuses of the aorta, which correspond to the position of the three semilunar cusps of the aortic valves.
The arch of the aorta forms an upward convexity, running from front to back to be continuous with the descending aorta. A small constriction can be seen at the junction of the arch with the descending aorta; it is called the aortic isthmus. The arch of aorta gives rise to three large arteries; the brachiocephalic trunk, the left common carotid artery, and the left subclavian artery.
The descending aorta is the continuation of the arch of the aorta. It runs from the level of the third and fourth thoracic vertebra to that of the fourth lumbar vertebra, where it forks into the right and left common iliac artery. Just before it divides into the common iliacs, it gives off the median sacral artery, which arises from its posterior side. The portion of the aorta that stretches from the third thoracic vertebra to the diaphragm is called the thoracic aorta, while the part that runs from the diaphragm until the fourth lumbar vertebra is called abdominal aorta.
Below, schematic image of the aorta, where you can see its portions and its branches.
