The aorta is both the main artery of the body and the largest artery in the body. It acts as the central supply source of oxygenated blood flow throughout the body and plays a large role in circulation. Beginning at the heart's left ventricle, the aorta travels upwards, slightly over and then down through the abdomen, where it branches off into the left and right iliac arteries that run through the legs. The aorta is often referred to in divided sections called the ascending aorta, the aortic arch, the thoracic or descending aorta and the abdominal aorta.
The ascending aorta is the section that goes up directly from the heart. The aortic arch is the part that arches slightly back and over the left lung. As it goes down again through the thorax, it becomes the thoracic, or descending, aorta and then the abdominal aorta before it divides into the iliac arteries. The aorta also branches off into smaller arteries that travel to the neck, the head and the arms, which essentially supply the body's major organs and tissues with oxygenated blood.
Like a network of tunnels that the heart pumps blood into, the aorta acts as the center of blood flow supply and the origin of all other major arteries including the carotid artery and the pulmonary artery. The aortic valve controls the blood flow pumped into the aorta and prevents oxygenated blood from reentering the left ventricle.
Problems with the aorta are often the result of a heart defect at birth, but they can also develop over time. It is not uncommon for the aortic valve to work improperly in newborns and preemies. Sometimes, the heart defect is outgrown and other times, surgical repair is necessary. Narrowing of the aorta and other arteries is not uncommon and is often the cause of poor circulation.
The aorta is the main trunk of a series of vessels which convey the oxygenated blood to the tissues of the body for their nutrition. It commences at the upper part of the left ventricle, where it is about 3 cm. in diameter, and after ascending for a short distance, arches backward and to the left side, over the root of the left lung; it then descends within the thorax on the left side of the vertebral column, passes into the abdominal cavity through the aortic hiatus in the diaphragm, and ends, considerably diminished in size (about 1.75 cm. in diameter), opposite the lower border of the fourth lumbar vertebra, by dividing into the right and left common iliac arteries. Hence it is described in several portions, viz., the ascending aorta, the arch of the aorta, and the descending aorta, which last is again divided into the thoracic and abdominal aortæ.
The ascending aorta is about 5 cm. in length. It commences at the upper part of the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum; it passes obliquely upward, forward, and to the right, in the direction of the heart’s axis, as high as the upper border of the second right costal cartilage, describing a slight curve in its course, and being situated, about 6 cm. behind the posterior surface of the sternum. At its origin it presents, opposite the segments of the aortic valve, three small dilatations called the aortic sinuses. At the union of the ascending aorta with the aortic arch the caliber of the vessel is increased, owing to a bulging of its right wall. This dilatation is termed the bulb of the aorta, and on transverse section presents a somewhat oval figure. The ascending aorta is contained within the pericardium, and is enclosed in a tube of the serous pericardium, common to it and the pulmonary artery.
The ascending aorta is covered at its commencement by the trunk of the pulmonary artery and the right auricula, and, higher up, is separated from the sternum by the pericardium, the right pleura, the anterior margin of the right lung, some loose areolar tissue, and the remains of the thymus; posteriorly, it rests upon the left atrium and right pulmonary artery. On the right side, it is in relation with the superior vena cava and right atrium, the former lying partly behind it; on the left side, with the pulmonary artery.
The only branches of the ascending aorta are the two coronary arteries which supply the heart; they arise near the commencement of the aorta immediately above the attached margins of the semilunar valves.
(A. coronaria [cordis] dextra) arises from the right anterior aortic sinus. It passes at first between the conus arteriosus and the right auricula and then runs in the right portion of the coronary sulcus, coursing at first from the left to right and then on the diaphragmatic surface of the heart from right to left as far as the posterior longitudinal sulcus, down which it is continued to the apex of the heart as the posterior descending branch. It gives off a large marginal branch which follows the acute margin of the heart and supplies branches to both surfaces of the right ventricle. It also gives twigs to the right atrium and to the part of the left ventricle which adjoins the posterior longitudinal sulcus.
(A. coronaria [cordis] sinistra), larger than the right, arises from the left anterior aortic sinus and divides into an anterior descending and a circumflex branch. The anterior descending branch passes at first behind the pulmonary artery and then comes forward between that vessel and the left auricula to reach the anterior longitudinal sulcus, along which it descends to the incisura apicis cordis; it gives branches to both ventricles. The circumflex branch follows the left part of the coronary sulcus, running first to the left and then to the right, reaching nearly as far as the posterior longitudinal sulcus; it gives branches to the left atrium and ventricle. There is a free anastomosis between the minute branches of the two coronary arteries in the substance of the heart.