Anatomy study note · Abdomen

Internal oblique

The middle of the three flat muscles of the anterolateral abdominal wall, lying deep to the external oblique with most of its fibres at right angles to it.

Key points

• Lumbar fascia, iliac crest, lateral 2/3 of inguinal ligament → lower 3 ribs, linea alba, pubis.
• T7–T12 + iliohypogastric + ilioinguinal (L1).
• Conjoint tendon with transversus; gives the cremaster.
• Aponeurosis splits round rectus above the arcuate line.
• 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. 700–702, 706–709, 713
• 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

• Jejunum and ileum
• Kidney
• Large intestine
• Linea alba
• Liver
• Lumbar plexus
• Pancreas
• Peritoneum
• Portal vein
• Psoas major
• Pyramidalis
• Quadratus lumborum

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