Under the external obliques, the fibers of the internal obliques run perpendicular to those of the external obliques, having numerous places where they attach (begin) and insert (end) along the way.
The internal obliques help with side-bending and rotation of the spine and rib cage. Like the external obliques, they aid compression and forward bending of the abdominal area.
The internal and external obliques work together in trunk rotation.
Next: the transversus abdominis
