The aorta is about 3 cm in diameter at its origin from the left ventricle. It passes superiorly as the ascending aorta, turns posteriorly and to the left (arch of the aorta) at about the level of the fourth thoracic vertebra, and then passes inferiorly as the thoracic aorta to the diaphragm. Inferior to the diaphragm, it is called the abdominal aorta. It terminates by dividing into the common iliac arteries.

SEE: illus.MAJOR BRANCHES OF AORTA and VENA CAVAE.

The divisions of the aorta are as follows:

Ascending aorta (two branches): Two coronary arteries (right and left) provide blood supply to the myocardium.

Aortic arch (three branches): The brachiocephalic artery divides into the right subclavian artery, which provides blood to the right arm and other areas, and right common carotid artery, which supplies the right side of the head and neck. The left common carotid artery supplies the left side of the head and neck. The left subclavian artery provides blood for the left arm and portion of the thoracic area.

Thoracic aorta: Two or more bronchial arteries provide blood for bronchi. Esophageal arteries provide blood to the esophagus. Pericardial arteries supply the pericardium. Nine pairs of intercostal arteries supply blood for intercostal areas. Mediastinal branches supply lymph gland s and the posterior mediastinum. Superior phrenic arteries supply the diaphragm.

Abdominal aorta: The celiac artery supplies the stomach, liver, and spleen. The superior mesenteric artery supplies all of the small intestine except the superior portion of the duodenum. The inferior mesenteric artery supplies all of the colon and rectum except the right half of the transverse colon. The middle suprarenal branches supply the adrenal (suprarenal) gland s. The renal arteries supply the kidneys, ureters, and adrenals. The testicular arteries supply the testicles and ureter. The ovarian arteries (which correspond to internal spermatic arteries of the male) supply the ovaries, part of the ureters, and the uterine tubes. The inferior phrenic arteries supply the diaphragm and esophagus. The lumbar arteries supply the lumbar and psoas muscles and part of the abdominal wall musculature. The middle sacral artery supplies the sacrum and coccyx. The right and left common iliac arteries supply the lower pelvic and abdominal areas and the lower extremities.

illus.