Sacral Plexus

Overview

Location: Formed from ventral rami of L4, L5, S1, S2, S3, and S4 nerves.
Position: Lies in front of the pyriformis, deep to pelvic fascia, in the posterior wall of the true pelvis.

L4 Nerve: Shared by lumbar and sacral plexuses.
- Divides into lumbar and sacral contributions.
- Forms lumbosacral trunk with L5.
Lumbosacral Trunk: Contributes to sacral nerve formation.
- Separated from S1 by superior gluteal vessels.
- S1 and S2 separated by inferior gluteal vessels.

Superior Gluteal Nerve
- Origin: Dorsal divisions of L4, L5, S1.
- Path: Exits pelvis above the pyriformis with the superior gluteal artery.
Inferior Gluteal Nerve
- Origin: Dorsal divisions of L5, S1, S2.
- Path: Exits pelvis below the pyriformis with the inferior gluteal artery.
Nerve to Pyriformis
- Origin: Dorsal divisions of S1, S2.
Nerve to Quadratus Femoris
- Origin: Ventral divisions of L4, L5, S1.
Nerve to Obturator Internus
- Origin: Ventral divisions of L5, S1, S2.
Posterior Femoral Cutaneous Nerve
- Origin: Anterior and posterior divisions of S1, S2, S3.
- Function: Sensory nerve for posterior thigh, scrotum in males, labia in females.
Pudendal Nerve
- Origin: Ventral divisions of S2, S3, S4.
Perforating Cutaneous Nerve
- Origin: Dorsal divisions of S2, S3.
- Path: Descends on pyriformis, through sacrotuberous ligament.
Pelvic Splanchnic Nerves
- Origin: S2, S3, S4.
- Function: Provide parasympathetic outflow; involved in erection.
Sciatic Nerve
- Composed of common peroneal (dorsal divisions of L4, L5, S1, S2) and tibial (ventral divisions of L4, L5, S1, S2, S3) components.

The sacral plexus is crucial for innervation of the lower limb and pelvic structures, with multiple branches serving sensory and motor functions.
Each nerve has specific origins and pathways, often associated with specific muscular or skin regions.

These notes cover the main aspects and details of the sacral plexus and its branches, providing a comprehensive overview for study and reference.