Sacral plexus
Plexus sacralis
NervousNervesWhole bodyLeft and right
View left in 3D View right in 3D
- What it is
- A triangular sheet on the front of the piriformis muscle on the back wall of the pelvis, formed by the lumbosacral trunk (L4-L5) and the ventral rami of S1-S4. Its roots converge on the greater sciatic foramen, where the sciatic, gluteal, posterior femoral cutaneous and pudendal nerves leave the pelvis.
- Function
- Supplies the buttock muscles, the back of the thigh, everything below the knee, the pelvic floor and perineum, and the S2-S4 parasympathetic outflow to the pelvic organs.
- Size
- About 10 cm across; the roots converge into a band ~2 cm wide
- Clinical note
- Pelvic fractures, sacral tumours or a difficult childbirth can stretch it; the S2-S4 parasympathetic branches that control bladder emptying and erection are protected during rectal-cancer surgery.