Anatomy study note · Abdomen

Quadratus lumborum

A flat quadrilateral muscle of the posterior abdominal wall beside the lumbar vertebral column.

Key points

• Iliolumbar ligament + iliac crest → 12th rib + upper lumbar transverse processes.
• Lumbar plexus.
• Fixes the 12th rib; lateral flexion.
• Fascia on it forms the lateral arcuate ligament.
• Trunk muscles: from myotomes of the somites.
• Dorsal part → dorsal-ramus muscles; ventral part → ventral-ramus muscles.
• Skeletal muscle: multinucleated, peripheral nuclei, striated.
• Epimysium → perimysium → endomysium.

The full note in the atlas also covers

Features · Origin · Insertion · Action · Nerve supply · Histology · Development

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Written from

• Snell’s Clinical Anatomy by Regions, 10th ed., ch. 6, PDF pp. 748–750; ch. 2, PDF p. 160
• Inderbir Singh’s Human Embryology, ch. 7, PDF pp. 108–109
• BRS Cell Biology & Histology, 7th ed., ch. 8, PDF pp. 135–144

More from the abdomen

• Rectus abdominis
• Renal arteries and veins
• Spleen
• Stomach
• Superficial epigastric vessels
• Superior mesenteric artery
• Suprarenal gland
• Testicular vessels
• Testis
• Transverse colon
• Transversus abdominis
• Umbilical cord

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