Abdominal external oblique muscle

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The external oblique muscle (of the abdomen) (also external abdominal oblique muscle) is the largest and the most superficial of the three flat muscles of the lateral anterior abdomen.

[edit] Structure

The external oblique is situated on the lateral and anterior parts of the abdomen. It is broad, thin, and irregularly quadrilateral, its muscular portion occupying the side, its aponeurosis the anterior wall of the abdomen. In most humans (especially males), the oblique is not visible, due to subcutaneous fat deposits and the small size of the muscle.

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 muscle; 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.

The aponeurosis of the external oblique muscle forms the inguinal ligament. The muscle also contributes to the inguinal canal.

Just deep to the external oblique is the internal oblique muscle.

[edit] Innervation

The external oblique muscle is innervated by the lower intercostal nerves.

[edit] Actions

The external oblique functions to compress the abdominal cavity, which increases the intra-abdominal pressure. It also participates in both flexion and rotation of the vertebral column.

[edit] Additional images

Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the lumbodorsal fascia.	The subcutaneous inguinal ring.	Diagram of sheath of Rectus.	Diagram of a transverse section through the anterior abdomina wall, below the linea semicircularis.
Femoral sheath laid open to show its three compartments.	Transverse section through the middle of the first lumbar vertebra, showing the relations of the pancreas.	The left side of the thorax.	Surface anatomy of the front of the thorax and abdomen.

[edit] See also

• Layers of the abdominal wall

[edit] External link

• LUC exab
• GPnotebook 1335492666
• SUNY Anatomy Image 7061
• Cross section at UV pembody/body8a

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

es:Oblicuo mayor del abdomen ja:外腹斜筋