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
Frequently asked questions
What does the internal oblique do?
The internal oblique compresses the abdomen; flexes and rotates the trunk to the ipsilateral side.
What nerve innervates the internal oblique?
The internal oblique is innervated by the thoracoabdominal nerves (T7-T12), subcostal, and L1 (iliohypogastric/ilioinguinal).
Where does the internal oblique attach?
The internal oblique originates from the thoracolumbar fascia, iliac crest, and lateral inguinal ligament and inserts on the inferior borders of ribs 10-12, linea alba, and pubis (conjoint tendon).
What is the blood supply of the internal oblique?
The internal oblique is supplied by the lower posterior intercostal / deep circumflex iliac arteries.