To have an understanding of aortic diseases, it is imperative to have a good knowledge base in anatomy, physiology, and function of the normal aorta. The aorta is a large conductance blood vessel, often called the greatest artery, normally reaching 0.7 m in length and 3.5 cm in diameter. It arises from the heart, arches anterocranially and then posterocaudally, and descends caudally, terminating as it bifurcates into the right and left common iliac arteries. The aorta is divided into six segments: (1) the aortic root, (2) the sinotubular junction, (3) the ascending aorta, (4) the aortic arch, (5) the isthmus and descending thoracic aorta, and (6) the abdominal aorta (Fig. 22–1).
Segmental division of the aorta: the aortic root (light blue), the sinotubular junction (green), the ascending aorta (yellow), the aortic arch (dark blue), the isthmus and descending (thoracic) aorta (red), and the abdominal aorta (purple). This figure was published in Aortic Diseases: Clinical Diagnostic Imaging Atlas, Hutchinson SJ, copyright Elsevier 2009.
The aortic root originates at the aortic valve annulus level and extends to the sinotubular junction. Normal diameter of the aortic root (at the widest proximal portion, known as bulbous) is up to 3.5 cm. The bulbous portion of the aorta is subdivided into the sinuses of Valsalva. The site where the bulbous portion of the aorta meets the narrower tubular-shaped aorta is termed sinotubular junction. Effacement of this junction suggests annuloaortic ectasia and often is seen in patients with Marfan syndrome. The ascending aorta follows the sinotubular junction and extends to the right brachiocephalic artery. The ascending aorta is an intrapericardial structure, measuring approximately 5 cm in length and up to 3 cm in diameter. The aortic arch is extrapericardial and courses leftward anterior to the trachea and continues posterior to the left of the trachea and esophagus and gives rise to all three great vessels: the innominate artery (brachiocephalic trunk), left common carotid artery, and left subclavian artery (Fig. 22–2). The normal diameter of the aortic arch is up to 2.9 cm. Arch branch vessel variants and right-sided arches can sometimes be seen. The isthmus is the narrower portion of the aorta (by approximately 3 mm) between the left subclavian artery and ligamentum arteriosus, a remnant of the ductus arteriosus. Blunt traumatic deceleration injury, resulting in transection to the aorta often occurs at this site. The descending thoracic aorta begins at the ligamentum arteriosus and continues to the level of the diaphragm. The descending thoracic aorta gives rise to intercostal, spinal, and bronchial arteries. The abdominal aorta starts at the hiatus of the diaphragm and courses retroperitoneal to its bifurcation. Major branch vessels include celiac arteries, superior and inferior mesenteric arteries, and middle suprarenal, renal, and testicular or ovarian arteries. The diameter of the suprarenal abdominal aorta ...