Fourth layer of muscles of the sole of the foot

Question 1

Dorsal interossei

Answer 1

Origin:

• Sides of adjacent metatarsals

Insertion:

• Extensor hoods and bases of proximal phalanges of toes II to IV

Innervation:

• Lateral plantar nerve form tibial nerbe, first and second dorsal interossei also innervated by deep fibular nerve (S2, S3)

Function:

• Abduction of toes II and IV at metatartophalangeal joints;
• Resist extension of metatartophalangeal joints and flexion of interphalangeal joints

Question 2

Plantar interossei

Answer 2

Origin:

• Medial sides of metatarsals of toes III to V

Insertion:

• Extensor hoods and bases of proximal phalanges of toes III to V

Innervation:

• Lateral plantar nerve from tibial nerve (S2, S3)

Function:

• Adduction of toes III to V metatarsophalangeal joints;
• Resist extension of the metatarsophalangeal joints and flexion of the interphalangeal joints.