The Obliquus externus abdominis (External or descending oblique muscle), situated on the lateral and anterior parts of the abdomen, is the largest and the most superficial of the three flat muscles in this region.

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

It arises, by eight fleshy digitations, from the external surfaces and inferior borders of the lower eight ribs; these digitations are arranged in an oblique line which runs downward and backward, the upper ones being attached close to the cartilages of the corresponding ribs, the lowest to the apex of the cartilage of the last rib, the intermediate ones to the ribs at some distance from their cartilages.

The five superior serrations increase in size from above downward, and are received between corresponding processes of the Serratus anterior; the three lower ones diminish in size from above downward and receive between them corresponding processes from the Latissimus dorsi. From these attachments the fleshy fibers proceed in various directions.

Those from the lowest ribs pass nearly vertically downward, and are inserted into the anterior half of the outer lip of the iliac crest; the middle and upper fibers, directed downward and forward, end in an aponeurosis, opposite a line drawn from the prominence of the ninth costal cartilage to the anterior superior iliac spine.

See also

• Layers of the abdominal wall

External link

Abdomen | Muscles of the trunk | Musculus obliquus externus abdominis | Oblicuo mayor del abdomen | %E5%A4%96%E8%85%B9%E6%96%9C%E7%AD%8B