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Posterior Abdominal Wall Muscles Anatomy
Posterior Abdominal Wall Muscles Anatomy
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The posterior abdominal wall is supported by several important muscles that help stabilize the trunk, assist in breathing, and allow movement of the lower limbs.
These muscles lie deep in the abdomen, alongside the lumbar vertebrae and pelvis. Together, they play key roles in posture, hip movement, and protecting the organs located behind the peritoneum.
There are four main muscles in this region:
Iliacus
Psoas major
Psoas minor (only in about 60% of people)
Quadratus lumborum.
Psoas Major
Psoas Major
The psoas major is located near the midline of the posterior wall, beside the lumbar vertebrae. It flexes the thigh at the hip and helps bend the spine to the side.
Origin: Transverse processes and bodies of T12–L5 vertebrae.
Insertion: Lesser trochanter of the femur (after passing under the inguinal ligament).
Innervation: Anterior rami of L1–L3 nerves.
Iliacus
Iliacus
The iliacus is a fan-shaped muscle on the lower part of the posterior abdominal wall. It flexes and laterally rotates the thigh at the hip.
The iliacus is a fan-shaped muscle on the lower part of the posterior abdominal wall. It flexes and laterally rotates the thigh at the hip.
Origin: Iliac fossa and anterior inferior iliac spine.
Insertion: Joins with the psoas major tendon and attaches to the lesser trochanter of the femur.
Innervation: Femoral nerve (L2-L4).
Quadratus Lumborum
Quadratus Lumborum
The quadratus lumborum is located on the side of the posterior abdominal wall, behind the psoas major. It’s a thick, four-sided muscle. It extends and bends the spine to the side; it holds the 12th rib steady during breathing.
The quadratus lumborum is located on the side of the posterior abdominal wall, behind the psoas major. It’s a thick, four-sided muscle. It extends and bends the spine to the side; it holds the 12th rib steady during breathing.
Origin: Iliac crest and iliolumbar ligament.
Insertion: Transverse processes of L1–L4 and the lower edge of the 12th rib.
Innervation: Anterior rami of T12–L4 nerves.
Quick Reference Table: Muscle Name, Origin, Insertion & Innervation
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Psoas Minor
Psoas Minor
The psoas minor is missing in about half of people. When present, the psoas minor lies in front of the psoas major and assists slightly in bending the trunk forward (flexion). It doesn’t play a major role in hip movement.
Origin: Vertebral bodies of T12 and L1.
Insertion: Pectineal line of the pubic bone.
Innervation: Anterior rami of L1 spinal nerve.
Need a recap? Take a look at the Posterior Abdominal Wall Muscles anatomy notes here.
Need a recap? Take a look at the Posterior Abdominal Wall Muscles anatomy notes here.
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References
References
Gray, H. (2009). Anatomy of the human body, part 2 (LibriVox Volunteers, Narr.) [Audiobook]. LibriVox. https://librivox.org/anatomy-of-the-human-body-part-2-by-henry-gray/ (Original work published 1858)
J Gordon Betts, Desaix, P., Johnson, E., Johnson, J. E., Korol, O., Kruse, D., Poe, B., Wise, J., Womble, M. D., & Young, K. A. (2013). Anatomy & physiology. Openstax College, Rice University. https://openstax.org/details/books/anatomy-and-physiology
Based on OpenStax, Anatomy and Physiology (2013), licensed under CC BY 4.0.
Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.
Content paraphrased; adaptations were made.
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