The structures of the sole of the foot are usually described in layers from superficial to deep.

1st layer

This layer contains the only abductors of the first and fifth digit (abductor hallucis and abductor digiti minimi) and the short flexor of digits 2-5, the flexor digitorum brevis, which lies deep to and attaches (in part) to the plantar aponeurosis. We also see the terminal end of the medial and lateral plantar arteries and nerves near the digits.

2nd layer

This layer houses the quadratus plantae muscle, the tendons of the flexor digitorum longus, the lumbrical muscles, and the tendon of the flexor hallucis longus. In the posterior medial side of this layer, we can see the proximal portions of the medial and lateral plantar arteries and nerves.

3rd layer

The third layer of the sole includes muscles that primarily serve the great toe. These include the adductor hallucis and the two heads of the flexor hallucis brevis. The flexor digiti mini also resides in this plantar layer.

4th layer

The fourth layer contains the interossei muscles and the deep plantar arterial arch.