External Abdominal Oblique Muscle: The external abdominal oblique is the biggest and significant superficial of the four muscles and occupies on the sides and front of the abdomen. It is thick and thin with its muscular portion obtaining the side and it’s aponeurosis the anterior wall of the abdomen. It appears from the external surface and inferior borders of the lower eight ribs.
The fibers from lowest ribs pass nearly vertically downwards and are inserted into the anterior half of the iliac crest; the middle and upper fibers, directed inferiorly and anteriorly, end in an aponeurosis at roughly the mid-clavicular line and insert into xiphoid process, the linea alba, the pubic crest, and the pubic tubercle.
Nerve Supply of the External Abdominal Oblique
The lower six thoracic nerves and the iliohypogastric and ilioinguinal nerves.
Function of the External Abdominal Oblique
Both sides working together, the external obliques flex the vertebral column by pulling the pubis towards the xiphoid process. Performing unilaterally it results in ipsilateral side flexion and contralateral rotation of the trunk.