Sole of foot – Second layer muscles
This specimen shows the muscles and tendons of the second layer of the sole of the foot.
The two intrinsic muscles, namely, the flexor digitorium accessorius and the lumbricals, and the two extrinsic tendons, namely, the flexor digitorum longus and the flexor hallucis longus, are present in the second layer of the sole of foot.
Flexor digitorum accessorius:
The flexor digitorum accessorius is an intrinsic muscle of the foot. It takes origin from the calcaneum and inserts into the tendon of flexor digitorum longus. It is supplied by the lateral plantar nerve. It supports and facilitates the action of flexor digitorum longus.
The four small, worm-like muscles, known as the lumbricals, are attached to the tendon of the flexor digitorum longus and to the lateral four toes. First lumbrical is supplied by the medial plantar nerve and the remaining three are supplied by the lateral plantar nerve. They cause plantar flexion of the toes at the metatarsophalangeal joint and extension at the interphalangeal joint.
Flexor digitorum longus:
The flexor digitorum longus takes origin from the tibia. Its tendon passes deep to the flexor retinaculum and enters the sole of the foot and splits into four to insert into the lateral four digits. It is supplied by the tibial nerve. The tendons cause plantar flexion of the lateral four digits.
Flexor hallucis longus:
The flexor hallucis longus takes origin from the fibula. Its tendon passes deep to the flexor retinaculum and enters the sole of the foot to inert into the great toe. It is supplied by the tibial nerve. It causes plantar flexion of the great toe.