LUMBAR & SACRAL PLEXUS

Lumbar Plexus

1. Definition A network of nerves formed by the anterior rami of L1 to L4 spinal nerves.

2. Location Found in the posterior abdominal wall, inside the psoas major muscle.

3. Formation L1, L2, L3, L4 anterior rami join to form the plexus.

4. Branches a. Iliohypogastric nerve (L1) b. Ilioinguinal nerve (L1) c. Genitofemoral nerve (L1–L2) d. Lateral femoral cutaneous nerve (L2–L3) e. Femoral nerve (L2–L4) f. Obturator nerve (L2–L4)

5. Functions a. Supplies skin of lower abdomen, thigh, and genital region b. Supplies muscles of anterior and medial thigh c. Important for walking, standing, and leg movements

6. Clinical importance Injury causes weakness in thigh movement, loss of sensation over thigh, difficulty in walking

Sacral Plexus

1. Definition A large nerve network formed by the anterior rami of L4, L5, S1, S2, and S3.

2. Location Present inside the pelvis, in front of the piriformis muscle.

3. Formation L4 and L5 join to form lumbosacral trunk → joins S1, S2, S3 to form sacral plexus.

4. Branches a. Sciatic nerve (L4–S3) b. Pudendal nerve (S2–S4) c. Superior gluteal nerve (L4–S1) d. Inferior gluteal nerve (L5–S2) e. Posterior femoral cutaneous nerve (S1–S3) f. Nerves to piriformis, obturator internus, quadratus femoris

5. Functions a. Supplies muscles of back thigh, leg, and foot b. Controls movements like walking, running, bending, lifting c. Supplies pelvic organs and perineum (via pudendal nerve)

6. Clinical importance a. Sciatica due to nerve compression causing leg pain b. Weakness of hip and leg muscles c. Loss of sensation in lower limb