Posterior Ramus of Third Sacral Nerve (Left)

Origin

The posterior ramus of third sacral nerve originates as one of two terminal branches of the third sacral nerve, the other being the anterior ramus.

Course

The posterior ramus emerges from the posterior sacral foramen and is covered at its exit by the multifidus muscle in the back. It divides into medial and lateral branches.

Branches

The medial branch is small and ends in the multifidus muscle.

The lateral branch joins with branches of the fifth lumbar nerve (L5) and all other posterior sacral rami to form loops posterior to the sacrum. Branches from these loops run posterior to the sacrotuberous ligament and form a second series of loops under gluteus maximus. Two or three gluteal branches arise from here and pierce the gluteus maximus (along a line from the posterior superior iliac spine to the coccygeal apex) to innervate the posterior gluteal skin.

Supplied Structures

The medial branch supplies motor innervation to the multifidus muscle. The lateral branch supplies sensory cutaneous innervation to the posterior gluteal skin (middle cluneal nerve).