Overview
This lecture covers the anatomy, groups, origins, insertions, functions, and innervation of the muscles of the foot, organized by their anatomical location.
Muscle Groups of the Foot
- Muscles of the foot are divided into: dorsal, medial, lateral, middle groups, interossei (dorsal/plantar), and lumbricals.
- Each group contains specific muscles with defined origins, insertions, and functions.
Dorsal Group (Extensors)
- Consists of extensor digitorum brevis and extensor hallucis brevis.
- Both originate from the calcaneus and are innervated by the deep fibular nerve.
- Extensor digitorum brevis extends the 2nd–4th toes.
- Extensor hallucis brevis extends the big toe.
Medial Group (Hallucis Muscles)
- Includes adductor hallucis, flexor hallucis brevis, and abductor hallucis.
- All are innervated by the tibial nerve.
- Adductor hallucis adducts and flexes the big toe.
- Flexor hallucis brevis flexes the big toe.
- Abductor hallucis abducts and flexes the big toe.
Lateral Group (Digiti Minimi Muscles)
- Includes flexor digiti minimi brevis, opponens digiti minimi, and abductor digiti minimi.
- All originate from the fifth metatarsal or calcaneal tuberosity and long plantar ligament.
- Flexor digiti minimi brevis flexes the little toe.
- Opponens digiti minimi adducts and opposes the little toe.
- Abductor digiti minimi abducts and flexes the little toe.
Middle Group
- Contains flexor digitorum brevis and quadratus plantae.
- Both help maintain the longitudinal arch and are innervated by plantar nerves.
- Flexor digitorum brevis flexes the 2nd–5th toes at the middle and proximal phalanges.
- Quadratus plantae assists in toe flexion.
Interossei Muscles
- Plantar interossei (3 muscles) adduct and flex the 3rd–5th toes toward the 2nd toe.
- Dorsal interossei (4 muscles) abduct the 2nd–4th toes away from the 2nd toe.
Lumbricals
- Four muscles originating from the flexor digitorum longus tendons.
- Insert at bases of proximal phalanges and extensor tendons of the 2nd–5th toes.
- Allow flexion of proximal phalanges and extension of middle/distal phalanges.
Key Terms & Definitions
- Abduction — movement away from the midline (2nd toe) of the foot.
- Adduction — movement toward the midline (2nd toe) of the foot.
- Flexion — bending or decreasing the angle of a joint.
- Extension — straightening or increasing the angle of a joint.
- Phalanx — bone segment of a finger or toe.
- Plantar aponeurosis — thick connective tissue of the foot’s sole.
- Calcaneus — heel bone.
Action Items / Next Steps
- Review muscle origins, insertions, functions, and innervation.
- Study diagrams to visualize each muscle’s location.
- Be able to identify and describe each group’s main functions.