What nerves innervate the posterior abdominal wall?

The posterior abdominal wall is innervated by the subcostal nerve (T12), the lumbar plexus (from ventral rami L1–L4), and the lumbar sympathetic chains. These supply muscles, skin, pelvic organs, and parts of the lower limb.

What is the lumbar plexus and how is it formed?

The lumbar plexus is a network of nerves formed within the psoas major muscle by the ventral rami of spinal nerves L1–L3 and the upper part of L4. The lower part of L4 joins L5 to form the lumbosacral trunk, connecting to the sacral plexus.

What are the main branches of the lumbar plexus?

The main branches include the iliohypogastric (L1), ilioinguinal (L1), genitofemoral (L1, L2), lateral cutaneous nerve of thigh (L2, L3), femoral nerve (L2–L4), obturator nerve (L2–L4), and accessory obturator (L3, L4, inconstant).

What does the genitofemoral nerve innervate?

The genitofemoral nerve divides into two branches: the genital branch enters the inguinal canal to supply the cremaster muscle and genital skin, and the femoral branch passes into the femoral sheath to supply skin over the femoral triangle.

What is the role of the subcostal nerve?

The subcostal nerve (T12) enters the abdomen posterior to the lateral arcuate ligament and courses anterior to the quadratus lumborum. It pierces the transversus abdominis aponeurosis to innervate parts of the anterior abdominal wall.

How does the femoral nerve course and what does it supply?

The femoral nerve emerges lateral to the psoas, passes between the psoas and iliacus, and enters the thigh deep to the inguinal ligament. It supplies the iliacus muscle and major anterior thigh structures.

What is the nervus furcalis and why is it important?

The nervus furcalis refers to spinal nerve L4 because it connects both the lumbar and sacral plexuses. Its upper part contributes to the lumbar plexus, while its lower part forms the lumbosacral trunk for the sacral plexus.

Lumbar Plexus – Posterior Abdominal Wall Nerves

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