Five muscles form the anterolateral group of the abdominal muscles, and they can be divided into two main groups - flat and vertical muscles.

There are three flat muscles with fibers beginning posterolaterally, passing anteriorly, and being replaced by an aponeurosis as the muscles continue toward the midline.

These are the:

• External abdominal oblique muscle
• Internal abdominal oblique muscle
• Transversus abdominis muscle

There are two vertical muscles located near the midline and enclosed within a tendinous sheath formed by the aponeuroses of the flat muscles (known as the rectus sheath).

These muscles are the:

• Rectus abdominis
• Pyramidalis

The linea alba is a fusion site of three pairs of abdominal anterolateral muscle aponeuroses. It is formed by the aponeuroses of the external and internal abdominal oblique muscles and transversus abdominis muscle. It stretches between the xiphoid process of the sternum and the pubic symphysis.