Final answer:
The medial plantar nerve innervates the plantar group muscles of the foot, which aid in supporting the foot's arch and in toe movements.
Step-by-step explanation:
The major muscle innervation of the medial plantar nerve includes the muscles of the plantar group, which has a four-layered group of intrinsic foot muscles. The plantar group is responsible for support and movements of the foot and toes. The first layer includes the abductor hallucis, the flexor digitorum brevis, and the abductor digiti minimi. The second layer contains the quadratus plantae and lumbricals, the third layer is composed of the flexor hallucis brevis, adductor hallucis, and the flexor digiti minimi brevis, and the fourth layer has the dorsal and plantar interossei. Together, they contribute to the flexion, abduction, and extension of the toes at the metatarsophalangeal and interphalangeal joints.