Anatomy
Origin:
Muscular digitations from the external inferior borders of the 5th to 12th ribs.
Insertion:
Via aponeurosis to the linea alba and the lateral lip of the iliac crest.
Key relations:
-Largest and most superficial of the three flat abdominal muscles.
-Helpful to visualise the directions of the fibres as a putting your hands on your pockets movement i.e. muscle fibres run inferomedially.
Functions
-Compresses abdominal cavity and raises intrabdominal pressure e.g. raking leaves.
-More limited role in flexion (contracting bilaterally) and rotation (contracting unilaterally) of the vertebral column (trunk).
Supply
Nerve Supply:
Anterior rami of thoracic spinal nerves (T7 to T12).
Blood Supply:
Superiorly by: lower intercostal arteries.
Inferiorly by: either the deep circumflex iliac or iliolumbar artery.
Clinical
The aponeurosis of external oblique forms the anterior wall of the inguinal canal and may be involved in hernia. The superficial inguinal ring is an opening in this abdominal layer.
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