Anatomy of the muscles and nerves of the posterior abdominal wall

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Muscles and Nerves of the Posterior Abdominal Wall

Figure 1. Anterior view of the muscles and nerves of the posterior abdominal wall.
Figure 2. Anterior view of the A. fascia covering the muscles of the posterior abdominal wall, and the B. path of the subcostal nerve.
 
Figure 3. Anterior view of the A. path of the iliohypogastric and ilioinguinal nerves, and the B. path of the genitofemoral nerve.
Figure 4. Anterior view of the A. path of the lateral cutaneous nerve of the thigh, and the B. path of the femoral nerve.
Figure 5. Anterior view of the path of the obturator and accessory obturator nerves.
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Preguntas

Preguntas del estilo USMLE Step 1

de completadas

Several students are studying the peripheral nervous system in a cadaver. One nerve is identified to originate from the anterior rami of L2 to L4. This nerve then runs along with the psoas muscles. An image of the nerve is shown below:


Which of the following statements regarding this nerve is most accurate? 

Transcript

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The posterior abdominal wall is a complex area of the body made up of muscles, vessels and nerves that work together to hold abdominal organs in place, adjust our posture, stabilize the hip joint and even flex our thighs on leg day!

The main paired muscles of the posterior abdominal wall include psoas major, iliacus and quadratus lumborum; and naturally, for those muscles to work properly, they receive innervation from various nerves.

Okay, now let’s take a closer look at these muscles! First up is the psoas major, which is a long, thick muscle that lies lateral to the lumbar vertebrae. It originates superiorly on the transverse processes of the bodies, and adjacent intervertebral discs of the T12 through L5 vertebrae.

The psoas major passes inferolaterally, deep to the inguinal ligament in order to insert on the lesser trochanter of the femur. Finally, approximately half the population has a psoas minor muscle that sits on the anterior aspect of each psoas major muscle.

Now, the psoas major muscle is covered by the psoas fascia or the psoas sheath, which is attached medially to the lumbar vertebrae and pelvic brim. The psoas sheath is thickened superiorly forming the medial arcuate ligament.

Inferior to the iliac crest, the psoas fascia is continuous with the part of the iliac fascia that covers the iliacus muscle.

When acting inferiorly with the iliacus muscle, the psoas muscle flexes and laterally rotates the thigh and when it acts superiorly it causes lateral flexion of the vertebral column.

When sitting, the psoas muscle acts with the iliacus muscle to flex the trunk. The innervation of the psoas major muscle comes from the anterior rami of the L1, L2 and L3 spinal nerves.

Fuentes

  1. "Raj's Practical Management of Pain" Mosby (2007)
  2. "Anatomical Variations of the Lumbar Plexus: A Descriptive Anatomy Study with Proposed Clinical Implications" Journal of Manual & Manipulative Therapy (2009)
  3. "Nerves and Nerve Injuries" Academic Press (2015)
  4. "Caring in Emergencies" Churchill Livingstone (1994)
  5. "Gray's Anatomy" Churchill Livingstone (2007)
  6. "Easy Injections" Elsevier Health Sciences (2006)
  7. "Nerves and Nerve Injuries" Academic Press (2015)
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