Anatomy study note · Pelvis
Sacral plexus
The nerve plexus on the front of piriformis, formed by the lumbosacral trunk (L4, L5) and the anterior rami of S1–S4. It supplies the buttock, most of the lower limb, the perineum and the pelvic viscera.
Key points
- L4–S4 on piriformis.
- Sciatic (L4–S3) = largest nerve.
- Superior gluteal → gluteus medius/minimus + TFL; inferior gluteal → gluteus maximus.
- Pudendal S2–S4; pelvic splanchnics S2–S4 (parasympathetic).
- Upper limb nerves: C4–T2 segments; lower limb: L2–S2.
- Ventral root: basal-lamina neurons. Dorsal root: neural-crest ganglion cells.
- Nerve: epineurium → perineurium (blood–nerve barrier) → endoneurium.
- Cut nerve: Wallerian degeneration; regrows 0.5–3 mm/day.
The full note in the atlas also covers
Relations · Branches · Histology · Development · Clinical notes
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Written from
- Snell’s Clinical Anatomy by Regions, 10th ed., ch. 8, PDF pp. 1044–1050
- Inderbir Singh’s Human Embryology, ch. 17, PDF pp. 318, 321, 323–325, 345–346; ch. 10, PDF pp. 143–144
- BRS Cell Biology & Histology, 7th ed., ch. 9, PDF pp. 163–166, 171–172
More from the pelvis
- Sacrococcygeal joint
- Sacroiliac joint
- Sacrotuberous and sacrospinous ligaments
- Sacrum
- Seminal vesicle
- Sigmoid colon
- Urinary bladder
- Uterine artery
- Uterine tube
- Uterus
- Vagina
- Coccygeus
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