Abdomen

Question 1

What are the nerves of the lumbar plexus

What are their courses?

Answer 1

Ilio-hypogastric
- Arise from anterior ramus of L1
- Emerge at the lateral border of psoas
- Slope across quadratus lumborum
- Pierce through transversus abdominis to continue in the neurovascular plan.
- Pierces internal oblique above the ASIS.
- Pierces external oblique about 2.5cm above the external ring and supplies suprapubic skin.

Ilio-inguinal
- Runs parallel to the ilio-hypogastric nerve but below it.
- It pierces the internal oblique and thus runs in the inguinal canal just below external oblique (you see if when you open external oblique)
- Its emerges through the superficial ring covered in external spermatic fascia to supply the anterior 1/3 of the scrotum and root of the penis, upper and medial part of the groin.

Lateral femoral cutaneous nerve
- Formed from the anterior rami of L2-L3.
- Passes on the surface of iliacus, deep to the fascia, posterior to the caecum
- Passes below ASIS 1cm medial
- Supplies the parietal peritoneum in the iliac fossa.

Femoral nerve
- Anterior rami of L2-L4.
- Passes in the gutter between psoas and iliacus.
- Leaves the iliac fossa by passing beneath the inguinal ligament lateral to the femoral sheath.

Genitofemoral nerve
- Formed in psoas major from L1-2
- It runs down deep to psoas fascia.
- On the left side it is overlaid by the ureter, gonadal vessels, ascending branch of left colic artery, and IMV.
- On the right side the gonadal, ureter, and ileocolic artery overlay it.
- Just above the inguinal ligament, it divides into genital and femoral branches.
- The genital branch passes through the deep ring with the cord structures and supplies motor branches to the cremaster muscle, sensory fibers to spermatic fascia, tunica vaginalis of the testis, and a small area of skin of the scrotum in males, and mons pubis in females.

Obturator
- Provides sensation to the medial thigh
- Motor to the adductor muscles of the thigh.