Extensor Hallucis Brevis Muscle – Nerve Supply, Function

Extensor Hallucis Brevis Muscle is a muscle on the top of the foot that helps to extend the big toe. Extensor hallucis brevis is a short muscle located in the dorsum of the foot, attaching between the calcaneus and proximal phalanx of the big toe (hallux). Along with the extensor digitorum brevis, it belongs to the group of dorsal foot muscles. Sometimes, the fibers of these two muscles fuse, making a single muscle that extends the toes. Working in synergy with the extensor hallucis longus, the main function of this muscle is to assist in the extension of the big toe at the metatarsophalangeal joint.

Structure

The extensor hallucis brevis is essentially the medial part of the extensor digitorum brevis muscle. Some anatomists have debated whether these two muscles are distinct entities. The extensor hallucis brevis arises from the calcaneus and inserts on the proximal phalanx of the digit 1 (the big toe).

Origin and Insertion

The short and slender extensor hallucis brevis muscle sits in the lateral aspect of the dorsum of the foot. It originates from the superior aspect of the calcaneus, just posteriorly to the calcaneocuboid joint. It courses medially over the dorsum of the foot, giving off a tendon that inserts onto the base of proximal phalanx of the hallux.

Nerve Supply of Extensor Hallucis Brevis Muscle

Nerve supplied by a lateral terminal branch of Deep Peroneal Nerve (deep fibular nerve) (proximal sciatic branches S1, S2). Same innervation of Extensor Digitorum Brevis

Function

The extensor hallucis brevis helps to extend the big toe.

Acting together with the extensor hallucis longus, this muscle extends the hallux at the metatarsophalangeal joint. This action results in returning the hallux from the flexed into the neutral position, or in pulling it above the ground if the contraction continues (hyperextension). This movement is important in gait, as raising the big toe clear of the ground facilitates walking and running.

References

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