Muscle · Core

External oblique

Musculus obliquus externus abdominis

The outermost and largest sheet of the abdominal wall, its fibres running downward and forward from the lower ribs toward the midline and the pelvis — the direction you would put your hands INTO your front pockets. It interlocks with serratus anterior and latissimus dorsi along the ribs, so the abdominal wall and the shoulder blade are mechanically continuous. The founder's document gives it trunk rotation to the OPPOSITE side plus flexion: the left external oblique turns you to the right. Its lower border rolls under to form the inguinal ligament.