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| Abdominal external oblique muscle | |
|---|---|
 Muscles of the trunk. | |
 The abdominal external oblique muscle | |
| Details | |
| Origin | Ribs 5-12 |
| Insertion | Xiphoid process, outer lip of theiliac crest,pubic crest,pubic tubercle,linea alba,inguinal ligament,anterior superior iliac spine (ASIS) |
| Nerve | Thoraco-abdominal nerves (T7-11) andsubcostal nerve (T12) |
| Actions | Flexion of thetorso and contralateral rotation of torso |
| Identifiers | |
| Latin | musculus obliquus externus abdominis |
| TA98 | A04.5.01.008 |
| TA2 | 2364 |
| FMA | 13335 |
| Anatomical terms of muscle | |
Theabdominal external oblique muscle (alsoexternal oblique muscle orexterior oblique) is the largest and outermost of the three flatabdominal muscles of the lateral anterior abdomen.
The external oblique is situated on the lateral and anterior parts of theabdomen. It is broad, thin, and irregularly quadrilateral, its muscular portion occupying the side, itsaponeurosis the anterior wall of the abdomen. In most humans, the oblique is not visible, due to subcutaneousfat deposits and the small size of the muscle.
It arises from eight fleshy digitations, each from the external surfaces and inferior borders of the fifth to twelfth ribs (lower eight ribs). These digitations are arranged in an oblique line which runs inferiorly and anteriorly, with the upper digitations 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 theserratus anterior muscle; the three lower ones diminish in size from above downward and receive between them corresponding processes from thelatissimus dorsi. From these attachments the fleshy fibers proceed in various directions. Its posterior fibers from the ribs to the iliac crest form a free posterior border.
Those from the lowest ribs pass nearly vertically downward, and are inserted into the anterior half of the outer lip of theiliac crest; the middle and upper fibers, directed downward (inferiorly) and forward (anteriorly), become aponeurotic at approximately themidclavicular line and form the anterior layer of the rectus sheath. This aponeurosis formed from fibres from either side of the external oblique decussates at thelinea alba.
Theaponeurosis of the external oblique muscle forms theinguinal ligament. The muscle also contributes to theinguinal canal.
Theinternal oblique muscle is just deep to the external oblique muscle.[1]
The external oblique muscle is supplied by ventral branches of the lower six thoracoabdominal nerves and the subcostal nerve on each side.
The cranial portion of the muscle is supplied by the lower intercostal arteries, whereas the caudal portion is supplied by a branches of either the deep circumflex iliac artery or the iliolumbar artery.
The external oblique functions to pull the chest downwards and compress the abdominal cavity, which increases the intra-abdominal pressure as in aValsalva maneuver. It also performs ipsilateral (same side) side-bending and contralateral (opposite side) rotation: the right external oblique would side-bend to the right and rotate to the left, and vice versa. The internal oblique muscle functions similarly except it rotates ipsilaterally.
Theoblique strain is a common baseball injury, particularly in pitchers. In both batters and pitchers it can affect the contralateral (leading) side external oblique, or the trailinginternal oblique.[2]
This article incorporates text in thepublic domain frompage 409 of the 20th edition ofGray's Anatomy(1918)
