The nn. spinales L4-S5 are shown on the right hand side, each giving a ramus anterior and ramus posterior. The plexus is formed by the rami anteriores of the nn. spinales L4-S4, while the S5 root (radix) joins the coccygeal (Co) root (radix) to form the plexus coccygeus. The rami anteriores of nn. spinales further split into divisiones anteriores and divisiones posteriores and numerous branches arise from each division. They then join together to form the nerves of the plexus sacralis, which can be divided into rami anteriores and posteriores. The rami anteriores are the n. musculi quadrati femoris, n. obturatoris interni, n. pudendalis, n. levatoris ani and n. musculi coccygei. The rami posteriores are the n. musculi piriformis, n. gluteus superior, n. cutaneus posterior femoris, n. cutaneus perforans and nn. splanchnici pelvici. Continuations of nn. spinales L4-S3 converge together to form a single terminal branch (ramus terminalis), known as the n. ischiadicus. It splits into the n. tibialis and n. fibularis communis to supply structures of the thigh, leg and foot.
