Descending Aorta
Aorta is a large blood vessel that comes out of the left side of the heart, taking away the oxygenated and nutrients rich blood to distribute to whole body.
For convenience of study it is divided into three parts; ascending aorta, arch of aorta and descending aorta. Hence descending aorta is the third and last part of the aorta and is the continuation of the arch of the aorta. It lies in the posterior mediastinum (central area in the chest between the lungs) in the thoracic cavity. It is divided into two parts; (according to its presence in the two large cavities of the body i.e. thoracic and abdominal) diaphragm is the reference point of this division. The part of descending aorta above the diaphragm is called descending thoracic aorta while its part below the diaphragm is called descending abdominal aorta.
read moreDescending Aorta
COURSE
It begins as the continuation of the arch of aorta (where it loops over the heart to begin its descent), on the left side of the lower border of the 4th thoracic vertebra. It descends with an inclination to the right and terminates at the lower border of the 12th thoracic vertebra, in the aortic opening in the diaphragm (here now onwards, it is called abdominal descending aorta) from where it runs downwards and slightly to the left in front of lumbar vertebrae, and ends in front of the lower part of 4th lumbar vertebra, by dividing into right and left common iliac arteries.
RELATIONS
Thoracic part:
At the commencement, it is situated to the left of vertebral column, it approaches median line as it descends and at its termination, it lies directly in front of vertebral column.
Anterior: root of left lung, heart, esophagus, and diaphragm. Posterior: vertebral column and hemiazygos veins. To the right: esophagus (in upper part), azygos vein, right lung and thoracic duct. To the left: left lung.
Abdominal part:
Posterior: to it are upper four lumbar vertebrae with their intervertebral disks. To the right: inferior vena cava, right crus of diaphragm. To the left: left crus of diaphragm, pancreas and duodenum.
BRANCHES
Thoracic part:
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Nine posterior intercostals arteries on each side (for the 3rd to 11th intercostal spaces)
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Two left bronchial arteries (for lungs)
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Esophageal branches (for esophagus)
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Pericardial branches (for posterior surface of the esophagus)
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Subcostal artery on each side (for abdominal wall)
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Mediastinal branches (for posterior mediastinum)
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Superior phrenic arteries (for diaphragm)
Abdominal part:
Ventral branches include celiac trunk, superior mesenteric artery and inferior mesenteric artery.
Lateral branches include right and left inferior phrenic, middle suprarenal, renal and testicular (in males) or ovarian (in females) arteries.
Dorsal branches include four pairs of lumbar arteries and a single median sacral artery.
Terminal branches as described above, includes the two common iliac arteries supplying the pelvis and lower limbs.
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