Final answer:
The rectus abdominis muscles originate at the pubic crest and symphysis, insert at the linea alba, and flex the vertebral column.
Step-by-step explanation:
The rectus abdominis is a pair of long, linear muscles located in the anterior abdominal wall. These muscles originate at the pubic crest and symphysis, and extend the length of the body's trunk. They are enclosed by the rectus sheath, a sheet of connective tissue. The rectus abdominis muscles insert at the linea alba, a white fibrous band that is made of the bilateral rectus sheaths, joining at the anterior midline of the body.
The action of the rectus abdominis is to flex the vertebral column, allowing movements such as curling the torso forward during a sit-up or bringing the ribcage closer to the pelvis. Additionally, the rectus abdominis helps with compression of the abdominal organs.