Internal oblique m.

The internal oblique muscle is the intermediate muscle of the abdomen, lying deep to the external oblique and just superficial to the transversus abdominal muscle.

Its fibers run perpendicular to the external oblique muscle, beginning in the thoracolumbar fascia of the lower back, the anterior 2/3 of the iliac crest (upper part of hip bone) and the lateral half of the inguinal ligament. The muscle fibers run from these point up and towards midline to the muscle's insertions on the inferior borders of the 10th through 12th ribs and the linea alba.

The internal oblique is innervated by the lower intercostal nerves, as well as the iliohypogastric nerve and the ilioinguinal nerve.