The posterior scrotal branches (in men) or ""posterior labial branches"" (in women) are two in number, medial and lateral. They are branches of the perineal nerve, which is itself is a branch of the pudendal nerve. The pudendal nerve arises from spinal roots S2 through S4, travels through the pudendal canal on the fascia of the obturator internus muscle, and gives off the perineal nerve in the perineum. The major branch of the perineal nerve is the posterior scrotal/posterior labial.

They pierce the fascia of the urogenital diaphragm

Urogenital diaphragm

Older texts have asserted the existence of an urogenital diaphragm, also called the triangular ligament, which was described as a layer of the pelvis that separates the deep perineal sac from the upper pelvis, lying between the inferior fascia of the urogenital diaphragm and superior fascia of the...

, and run forward along the lateral part of the urethral triangle in company with the posterior scrotal branches

Posterior scrotal branches

Posterior scrotal branches can refer to:* Posterior scrotal nerves* Posterior scrotal branches of the internal pudendal artery...

 of the perineal artery

Perineal artery

The perineal artery arises from the internal pudendal artery, and turns upward, crossing either over or under the Transversus perinæi superficialis, and runs forward, parallel to the pubic arch, in the interspace between the Bulbocavernosus and Ischiocavernosus, both of which it supplies, and...

; they are distributed to the skin of the scrotum

Scrotum

In some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...

 or labia and communicate with the perineal branch of the posterior femoral cutaneous nerve.

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