Muscle
Internal oblique
Middle flat abdominal muscle
High-yield
Fibres run perpendicular to external oblique; rotates the trunk to the SAME side. Contributes to the cremaster and conjoint tendon.
Overview
The intermediate flat muscle with fibres perpendicular to external oblique, contributing to the rectus sheath and the conjoint tendon.
Reference facts
- Origin
Thoracolumbar fascia, iliac crest, and lateral inguinal ligament
- Insertion
Inferior borders of ribs 10–12, linea alba, and pubis (conjoint tendon)
- Action
Compresses the abdomen; flexes and rotates the trunk to the ipsilateral side
- Innervation
Thoracoabdominal nerves (T7–T12), subcostal, and L1 (iliohypogastric/ilioinguinal)
- Blood supply
Lower posterior intercostal / deep circumflex iliac arteries