Muscles: Actions, Origins & Insertions Practice Test

The muscle in question is the rectus abdominis. It runs vertically on the front of the abdomen and attaches from the pubic crest and symphysis up to the xiphoid process and the costal cartilages of the lower ribs. When it contracts, it pulls the rib cage downward and toward the pelvis, which helps depress the ribs, while also shortening the distance between the sternum and pelvis to flex the vertebral column. At the same time, its tightening increases intra-abdominal pressure to help compress the abdomen, supporting movements like forced expiration, coughing, and childbirth. This combination of actions—depressing the ribs, flexing the spine, and compressing the abdomen—fits the rectus abdominis best. Other muscles in the options either act primarily on the hip or the shoulder girdle and do not combine all three functions.