Rectus abdominis

A large muscle in the front of the abdomen that assists in the regular breathing movement and supports the muscles of the spine while lifting and keeping abdominal organs such as the intestines in place. The rectus abdominis plays a key role in "sit-ups." Rectus means straight. The rectus abdominis is a straight abdominal muscle. It is sometimes simply called the rectus.

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rectus ab·dom·i·nis -ab-'däm-ə-nəs n a long flat muscle on either side of the linea alba extending along the whole length of the front of the abdomen, arising from the pubic crest and symphysis, inserted into the cartilages of the fifth, sixth, and seventh ribs, and acting to flex the spinal column, tense the anterior wall of the abdomen, and assist in compressing the contents of the abdomen