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Collateral Branch of Second Intercostal Nerve (Left)
Nervous System

Collateral Branch of Second Intercostal Nerve (Left)

Ramus collateralis nervi intercostalis secundi

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The collateral branches arise from the anterior rami of the thoracic nerves (or intercostal nerves) early in their course.


The collateral branches arise medial to the angles of the ribs. It courses along the intercostal space, following the superior border of the rib below and within the same muscular plane as the anterior ramus (or intercostal nerve). The collateral branches are accompanied by a collateral artery and vein, respectively.


There are no named branches of the collateral branches; however, they may rejoin the anterior ramus before it gives off its anterior cutaneous contribution.

Supplied Structures & Function

The collateral branches aid in supplying the intercostal muscles and parietal pleural of the lungs.

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Intercostal Nerve

ScienceDirect image

The intercostal nerve frequently runs within the middle of the intercostal space (73% of the time) and occasionally courses along the inferior aspect of the intercostal space just above the subjacent rib (Hardy, 1988).

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