It is broad, thin, and irregularly quadrilateral, its muscular portion occupying the side, its aponeurosis the anterior wall of the abdomen.

In most humans, the oblique is not visible, due to subcutaneous fat deposits and the small size of the muscle.

This aponeurosis formed from fibres from either side of the external oblique decussates at the linea alba.

The external oblique functions to pull the chest downwards and compress the abdominal cavity, which increases the intra-abdominal pressure as in a Valsalva maneuver.

[2] This article incorporates text in the public domain from page 409 of the 20th edition of Gray's Anatomy (1918)