Normal Anatomy

The aorta as a complete vessel commences at the upper part of the left ventricle, where it is about 3 cm in diameter. After ascending for a short distance, it 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.

Accepted practice is to divide the aorta into three distinct and arbitrary sections: the ascending aorta, the arch of the aorta, and the descending aorta. The descending aorta is then further divided into the thoracic aorta and the abdominal aorta.

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 axis of the heart, 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 three small dilatations called the aortic sinuses are present, opposite the segments of the aortic valve. 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 has a somewhat oval shape. The ascending aorta is contained within the pericardium, and is enclosed in a tube of serous pericardium, which is common to this and the pulmonary artery. Thus a rupture of the wall of the ascending aorta, as occurs for example in aortic dissection, may lead to a life threatening hemoperi-cardium, even if the rupture itself is not that dramatic. The only branches of the ascending aorta are the two coronary arteries which supply the heart; they arise near the start of the aorta immediately above the attached margins of the semilunar valves.

The arch of the aorta begins at the level of the upper border of the second sternocostal articulation of the right side. Initially the arch runs upward, backward, and to the left in front of the trachea. It then runs backwards on the left side of the trachea and finally passes downward on the left side of the body of the fourth thoracic vertebra, at the lower border of which it becomes continuous with the descending aorta. It thus forms two curvatures: one with its convexity upward, and the other with its convexity forward and to the left. Its upper border is usually about 2.5 cm below the superior border to the manubrium sterni. Three vessels branch off from the arch of the aorta: the innominate, the left common carotid, and the left subclavian [4].

In the fetal aorta, considerable narrowing of the lumen between the origin of the left subclavian artery and the attachment of the ductus arteriosus leads to formation of the aortic isthmus. Immediately beyond the ductus arteriosus the fetal aorta also presents a fusiform dilation termed the aortic spindle which is the point of junction of the two parts. This is marked in the arch concavity by an indentation or angle. These conditions may persist, to some extent, in the adult, where the average diameter of the spindle exceeds that of the isthmus by roughly 3 mm [5].

The thoracic aorta starts after the arch of the aorta and runs down to the diaphragm whereupon the abdominal aorta begins (Figs. 1,2). Numerous vessels branch off from the thoracic aorta to supply oxygenated blood to the chest cage and the organs within the chest. Like other sections of the aorta (the ascending aorta, aortic arch and abdominal aorta), the thoracic aorta is an arbitrary anatomic entity.

Arch Aorta

Fig. 1. Normal anatomy of the aorta in the thorax A Ascending aorta B Aortic arch

C Descending aorta (thoracic aorta)

1 Right coronary artery

2 Left coronary artery

3 Brachiocephalic trunk

4 Left common carotid artery

5 Left subclavian artery

6 Bronchial arteries

7 Right and left intercostal arteries

Fig. 1. Normal anatomy of the aorta in the thorax A Ascending aorta B Aortic arch

C Descending aorta (thoracic aorta)

1 Right coronary artery

2 Left coronary artery

3 Brachiocephalic trunk

4 Left common carotid artery

5 Left subclavian artery

6 Bronchial arteries

7 Right and left intercostal arteries

Fig. 2a, b. a Volume rendered CE MRA image of the normal anatomy of the aorta. Note the accurate depiction of the supraaortic vessels (Gd-BOPTA, 0.1 mmol/kg). b MIP reconstruction (lateral view of another CE MRA study (Gd-BOPTA, 0.1 mmol/kg)

Aorta Anatomy

Fig. 2a, b. a Volume rendered CE MRA image of the normal anatomy of the aorta. Note the accurate depiction of the supraaortic vessels (Gd-BOPTA, 0.1 mmol/kg). b MIP reconstruction (lateral view of another CE MRA study (Gd-BOPTA, 0.1 mmol/kg)

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Responses

  • gebre
    What is the vessel behind ascending aorta?
    8 years ago
  • Which two vessels branch from abdominal aorta?
    7 years ago

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