The sacral plexus arises from spinal roots L4-S4. Notice that the sacral and lumbar plexuses overlap. Because of this relationship, many fibers of the lumbar plexus contribute to the sacral plexus. Consequently, these two plexuses are frequently referred to as the lumbosaral plexus. The sacral plexus supplies the gluteal region, floor of the pelvis and the lower extremities. The largest nerve of the sacral plexus, and for that matter, the largest nerve in the body, is the sciatic nerve. It is formed from spinal roots L4-S3, and supplies the entire lower limb except the anteromedial thigh (femoral nerve). The sciatic nerve is actually two nerves, the tibial and common fibular (AKA common peroneal) which are wrapped together into a common sheath by connective tissue.
Sciatic: semimembranosus & semitendinosus
A. Tibial: long head biceps femoris, knee flexors, plantar flexors.
B. Fibular (peroneal): short head biceps femoris,fibularis muscles, tibialis anterior, toe extensors.
2. Pudendal (S2-S4): muscles of perineum, urogenital diaphragm, anal & urethral sphincters.