The common aorta or aortic trunk is the main systemic arterial trunk. It begins at the base of the left ventricle passes backwards and forwards between the pulmonary artery on the left and right atrium on the right (first part-ascending aorta), turns upwards and backwards inclining slightly to the left, thus describing a curve called the aortic arch with its convexity directed upwards and forwards. At its origin, the caliber is greatest forming the bulbus aortae and here it presents three dilatations, the sinuses of the aorta correspond to the cuspsof the aortic valve.
The aorta then reaches the level of the body of the seventh or eighth dorsal vertebra runs backwards as the thoracic aortabetween the lungs below the bodies of the dorsal vertebrae it lies slightly to the left of the median line, and reaches the hiatus aorticus.
It gradually diminishes in size still about the seventh or eighth dorsal vertebra but thereafter it rapidly diminishes in caliber.
Passing through the hiatus aorticus it enters the abdomen as the abdominal aorta, passes backwards below the bodies of the lumbar vertebrae and the psoas minor in contact with the left crus of the diaphragm and the ventral longitudinal ligament. About the fifth lumbar vertebra, it terminates by dividing into two internal iliac arteries.
In addition to its terminal branches, the common aorta gives off two collateral branches, the coronary or cardiac arteries.
Relations
- At its origin the aorta is related to the pulmonary artery on the left at the aortic arch. The thoracic aorta is related on its left to the lung, left pulmonary artery, left vagus and vena hemiazygos and on its right to the oesophagus and trachea.
- In theposterior mediastinum it is related to the lungs laterally and the bodies of dorsal vertebrae dorsally.
- The abdominal aorta is related dorsally to the bodies of lumbar vertebrae, ventral longitudinal ligament, tendon of left crus of diaphragm and psoas minor and ventrally to the pancreas and rumen; on its right to posterior vena cava and on its left to the left adrenal, left kidney and left ureter.
Collateral branches
- The aorta gives number of branches in its course as it run backwards through the thoracic and abdominal cavities; it is convenient to group them into two sets, branches of the thoracic aorta and abdominal aorta. The branches again divide into parietal and visceral.
- The parietal branches are distributed to the walls of the cavities, while the visceral ones are distributed to the organs contained in them. Some of these branches such as intercostals, lumbars, renals, spermatics (in the male) and utero-ovarian (in the female) are in pairs.
- The others are bronchial, oesophageal, phrenic, coeliac, anterior mesenteric, posterior mesenteric and sacro coccygeal arteries are unpaired.
