musculus obliquus internus abdominis

[TA] internal oblique muscle of abdomen: origin, inguinal ligament, iliac crest, thoracolumbar fascia; insertion, inferior three or four costal cartilages, linea alba, conjoined tendon to pubis; innervation, seventh to twelfth intercostal, first lumbar; action, flexes and rotates vertebral column, increases intra-abdominal pressure, acts as accessory respiratory muscle.