There are 4 muscles that make up your abdominal muscle anatomy: rectus abdominis, external oblique, internal oblique, and transverse abdominis.

Transversus Abdominis muscle. It's located deep to the External Abdominal Oblique and Internal Abdominal Oblique muscles.

There are actually four: The External oblique, internal oblique, rectus abdominis and the transversus abdominis.

External Oblique Internal Oblique Transversus Abdominis REctus Abdominis

There are two muscle pairs that help form the natural abdominal girdle The Internal Oblique and the Transversus Abdominis form the shape of the abdomen.