Sacral Plexus Flashcards
Site
In front of:
1. Sacrum
2. Piriformis
Behind:
1. Pelvic colon
2. Rectum
3. Ureter
4. Internal iliac artery
Roots and formation
- 5 roots
- Lumbosacral trunk:
Union of ventral rami L4 lower part & L5 - It leaves psoas major at its medial border below obturator nerve
- Descends over sacrum ala to pelvis
- Ventral rami of upper 3 sacral nerves and upper part of S4 ventral ramus
- Ventral rami of upper 4 sacral nerves emerge via anterior sacral foramina
- Upper part of L4 ventral ramus shares in lumbar plexus while lower part of S4 ventral ramus shares in coccygeal plexus, so L4 and S4 ventral rami called nervus furcalis
Branches to lower limb
Leaves through greater sciatic foramen
Branches:
1. Superior gluteal nerve (L4, 5 and S1)
2. Inferior gluteal nerve (L5, S1 and 2)
3. Nerve to quadratus femoris (L4, 5 & S1)
4. Nerve to obturator internus (L5, S1 & 2)
5. Posterior cutaneous nerve of thigh (S1, 2 & 3)
6. Sciatic nerve (L4, 5, S1, 2 & 3)
Superior gluteal nerve
Supplies gluteus medius, minimus and tensor fasciae latae
Inferior gluteal nerve
Supplies gluteus maximus
Nerve to quadratus femoris
Supplies:
1. Quadratus femoris
2. Inferior gemellus
Nerve to obturator internus
Supplies:
1. Obturator internus
2. Superior gemellus
Posterior cutaneous nerve of thigh
Supplies skin of buttock & thigh back
Largest branch of plexus & largest nerve in body
Branches to pelvic muscles and viscera and perineum
- Nerve to piriformis (S1 & 2)
- Pelvic splanchnic nerve (S2, 3 & 4): parasympathetic to pelvic viscera
- Pudendal nerve (S2, 3 & 4): leaves pelvis via greater sciatic foramen & re-enters it via lesser sciatic foramen
- Branches to levator ani, coccygeus & external anal sphincter (S4)
Perforating cutaneous nerve (S2 and S3)
Supplies skin of
buttock lower part
