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Rectus abdominis
origin
pubic crest and symphsis
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rectus abdominis
insertion
xiphoid process and costal cartilages of ribs 5-7
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rectus abdominis
action
- flex and rotate lumbar region of vertebral column;
- fix and depress ribs, stabilize pelvis during walking, increase intra-abdominal pressure;
- used in sit-up curls
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external oblique
origin
by fleshy strips from outer surfaces of lower 8 ribs
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external oblique
insertion
- most fibers insert into linea alba via a broad aponeurosis;
- some insert into pubic crest and tubercle and iliac crest
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external oblique
action
- when pair contract simultaneously, flex vertebral column and compress abdominal wall and increase intra-abdominal pressure;
- acting individually, aid muscles of back in rotating trunk and flexing laterally;
- used in oblique curls
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internal oblique
origin
lumbar fascia, iliac crest, and inguinal ligament
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internal oblique
insertion
linea alba, pubic crst, last three or four ribs, and costal margin
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internal oblique
action
as for external oblique
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transverses abdominis
origin
- inguinal ligament, lumbar fascial, cartilages of last 6 ribs;
- iliac crest
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transverse abdominis
insertion
linea alba, pubic crest
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transverses abdominis
action 
compresses abdominal contents
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