Dorsal branch of second posterior intercostal artery

The dorsal branch of the second posterior intercostal artery is a branch of the second posterior intercostal artery that arises from the costocervical trunk (rather than the aorta, which supplies the lower posterior intercostal arteries). It courses posteriorly to supply structures of the back in the region of the second intercostal space.

Origin and Course

The second posterior intercostal artery typically originates from the supreme (superior) intercostal artery, itself a branch of the costocervical trunk of the subclavian artery. As the second posterior intercostal artery travels along the inferior border of the second rib within the intercostal space, it gives off a dorsal branch that passes posteriorly toward the vertebral column and the muscles of the back.

Distribution and Supply

The dorsal branch divides into:

• A medial (spinal) branch, which enters the intervertebral foramen to supply the spinal cord, its meninges, and the vertebral body at that level.

• A lateral (muscular/cutaneous) branch, which supplies the deep muscles of the back (such as the erector spinae and transversospinalis groups), the overlying skin, and the periosteum of the adjacent vertebrae and ribs.