POSTERIOR INTERCOSTAL ARTERIES - Course , Relations , Branches || Dr G Bhanu Prakash

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POSTERIOR INTERCOSTAL ARTERIES
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The intercostal spaces are supplied by pairs of anterior and posterior intercostal arteries.

There are 11 pairs of intercostal arteries, Posterior Intercostal arteries supply greater part of the intercostal spaces.

The first and second intercostal spaces are supplied by the superior intercostal artery by its branches, and the remaining nine are supplied by separate branches from the descending thoracic aorta.

The superior intercostal artery is the descending branch of the costocervical trunk, arises from the second part of the subclavian artery

Right and left subclavian arteries classically have different origins:
right subclavian artery (RSA) is one of the terminal branches of the brachiocephalic artery

left subclavian artery (LSA) arises as the third branch of the aortic arch after the left common carotid artery

Course and Relations
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The right posterior intercostal arteries are longer than the left as a reason the descending aorta lies on the left side and anterior to the vertebral column.
Posterior intercostal arteries pass behind the oesophagus, thoracic duct, azygos vein, and sympathetic chain but anterior to the vertebral body .
left posterior intercostal arteries are smaller than right and runs behind the hemiazygos vein , sympathetic chain, but infront of the side of the vertebral body .
The posterior intercostal artery divides into the anterior and posterior ( dorsal ) rami.
In the intercostal space, the anterior rami of posterior intercostal artery runs between the intercostal vein (above) and the intercostal nerve (below).

Termination
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posterior intercostal arteries ends at the level of costochondral junction by anastomosing with the anterior intercostal artery . .

Branches
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1. Dorsal ( ramus ) branch: It supplies the spinal cord, vertebra and muscles, and skin of the back.
2. Collateral branch:
3. Muscular branches: supply intercostal, pectoral,and serratus anterior muscles.
4. Lateral cutaneous branch:
5. Mammary branches (external mammary arteries) : They arise from posterior intercostals arteries of the 2nd, 3rd, and 4th intercostal spaces and supply the breast mammary gland.
6. Right bronchial artery: It arises from right 3rd posterior intercostal artery.

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