External Oblique originates from which ribs?

External Oblique originates from which ribs?

• A. Ribs 1-8
• B. Iliac crest
• C. Ribs 5-12
• D. Pubis

Answer: (C)

External oblique originates from the external surfaces of the lower ribs, specifically ribs 5 through 12. The fibers angle downward and forward, and the broad aponeurosis that forms its end continues toward the midline to join the linea alba, while also giving attachments to the pubic crest and the iliac crest. This rib-range origin explains its position in the anterolateral abdominal wall and its actions: contracting on one side rotates the trunk to the opposite side and laterally flexes, while bilateral contraction increases abdominal pressure and assists with expiration. The iliac crest and pubis are not the primary origins; they are instead points where the external oblique’s aponeurosis attaches, and a upper rib range like 1–8 is not correct.

External oblique originates from the external surfaces of the lower ribs, specifically ribs 5 through 12. The fibers angle downward and forward, and the broad aponeurosis that forms its end continues toward the midline to join the linea alba, while also giving attachments to the pubic crest and the iliac crest. This rib-range origin explains its position in the anterolateral abdominal wall and its actions: contracting on one side rotates the trunk to the opposite side and laterally flexes, while bilateral contraction increases abdominal pressure and assists with expiration. The iliac crest and pubis are not the primary origins; they are instead points where the external oblique’s aponeurosis attaches, and a upper rib range like 1–8 is not correct.