Extensor hallucis longus muscle

The extensor hallucis longus muscle is a thin skeletal muscle, situated between the tibialis anterior and the extensor digitorum longus. It extends the big toe and dorsiflects the foot. It also assists with foot eversion and inversion.

Structure
The muscle ends as a tendon of insertion. The tendon passes through a distinct compartment in the inferior extensor retinaculum of foot. It crosses anterior tibial vessels lateromedially near the bend of the ankle. In the foot, its tendon is situated at along the medial side of the dorsum of the foot.  Opposite the metatarsophalangeal articulation, the tendon gives off a thin prolongation on either side, to cover the surface of the joint. An expansion from the medial side of the tendon is usually inserted into the base of the proximal phalanx.

Origin
The extensor hallucis longus muscle arises from the middle portion of  the anterior surface of the fibula and adjacent interosseous membrane of the leg.  Its origin is medial to the origin of the extensor digitorum longus muscle.

Insertion
The muscle inserts at the base of the distal phalanx of the great toe. 

Nerve supply
The muscle receives motor innervation from the deep fibular nerve (L5)  (a branch of common fibular nerve).

Relations
The anterior tibial vessels and deep fibular nerve pass between this muscle and the tibialis anterior muscle.

Variation
Occasionally united at its origin with the extensor digitorum longus.

The extensor ossis metatarsi hallucis, a small muscle, sometimes found as a slip from the extensor hallucis longus, or from the tibialis anterior, or from the extensor digitorum longus, or as a distinct muscle; it traverses the same compartment of the transverse ligament with the extensor hallucis longus.

Actions/movements
The muscle extends/dorsiflects the big toe (primary action), and dorsiflects the foot (secondary action).