Anatomy study note · Abdomen

Psoas major

A long muscle beside the lumbar vertebrae that passes behind the inguinal ligament into the thigh. With iliacus it forms the iliopsoas, the main flexor of the hip.

Key points

• T12–L5 → lesser trochanter (with iliacus).
• Lumbar plexus.
• Main hip flexor (iliopsoas).
• Psoas abscess → swelling below the inguinal ligament.
• Striated muscle: myotomes + local mesenchyme.
• Nerve supply indicates origin.
• 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 · Clinical notes

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Written from

• Snell’s Clinical Anatomy by Regions, 10th ed., ch. 6, PDF pp. 747–750
• Inderbir Singh’s Human Embryology, ch. 7, PDF pp. 92, 108–109
• BRS Cell Biology & Histology, 7th ed., ch. 8, PDF pp. 135–144

More from the abdomen

• Pyramidalis
• Quadratus lumborum
• Rectus abdominis
• Renal arteries and veins
• Spleen
• Stomach
• Superficial epigastric vessels
• Superior mesenteric artery
• Suprarenal gland
• Testicular vessels
• Testis
• Transverse colon

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