ORIGIN: Spinal cord segment T5.

COURSE/DISTRIBUTION: This nerve takes origin from spinal cord segment T5 and leaves the vertebral canal by passing through the intervertebral foramen between T5 and T6 vertebrae. It immediately divides into two rami- dorsal and ventral rami.

Dorsal ramus:

Immediately a turn backwards, close to T5 costotransverse joint and divides into medial and lateral branches.

bulletThe medial branch immediately passes between the joint and the superior costotransverse ligament with the corresponding intertransversarii. It runs between the semispinalis thoracis and multifidus. After supplying these muscles, it enters the rhomboideus major, minor and the trapezius. Its cutaneous branches now enter the skin at the side of T5 vertebra to supply the medial part of posterior aspect of T5 dermatome.
bulletThe lateral branch runs laterally and occupies the interval between the superior costotransverse ligament and the intertranversarii. It then turns on the medial aspect of the T5 levator costae. It runs between the longissimus thoracis and iliocostalis thoracis. Its muscular branches supply these muscles; it then pierces the skin of the remaining lateral part of the T5 dermatome to supply it with cutaneous branches.

Ventral ramus:

Continues as the fifth intercostal nerve, which runs in the costal groove of the 5th rib under the 5th posterior intercostal artery. The 5th superior anterior intercostal artery later replaces this artery in the same groove.


bulletCutaneous branches
bulletMuscular branches
bulletDorsal ramus
bulletVentral ramus
  1. Continues as 5th intercostal nerve.


Tip:  T1-T6 nerves have the same course.


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