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Origin: Ensiform cartilage; costal cartilages on either side and bony portions of 6 or 7 lower ribs; by the ligamenta arcuata interna and externa to the 2d lumbar vertebra and last rib; and by the crura to the 2d, 3d, and 4th lumbar vertebrae. Converges from all sides toward centre of muscle, with general direction also upward, so as to form a dome-shaped structure. Insertion: Central (or cordiform) tendon of muscle. Nerve: Two phrenic. Action: Expands cavity of chest by depressing floor of latter in the performance of abdominal inspiration; presses on abdominal viscera, and so facilitates vomiting, urination, defecation, and uterine contraction.