The extensor hallucis longus muscle is a thin skeletal muscle, situated between the

tibialis anterior The tibialis anterior muscle is a muscle in humans that originates along the upper two-thirds of the lateral (outside) surface of the tibia and inserts into the medial cuneiform and first metatarsal bones of the foot. It acts to dorsiflex and inve ...

and the

extensor digitorum longus The extensor digitorum longus is a pennate muscle, situated at the lateral part of the front of the leg. Origin and insertion It arises from the lateral condyle of the tibia; from the upper three-quarters of the anterior surface of the body of t ...

. It extends the big toe and dorsiflects the foot. It also assists with foot eversion and inversion.

Structure

The extensor hallucis longus muscle arises from the anterior surface of the

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity i ...

for about the middle two-fourths of its extent, medial to the origin of the extensor digitorum longus muscle. It also arises from the

interosseous membrane of the leg The interosseous membrane of the leg (middle tibiofibular ligament) extends between the interosseous crests of the tibia and fibula, helps stabilize the Tib-Fib relationship and separates the muscles on the front from those on the back of the le ...

to a similar extent. The anterior tibial vessels and deep fibular nerve lie between it and the tibialis anterior. The fibers pass downward, and end in a

tendon A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

, which occupies the anterior border of the muscle, passes through a distinct compartment in the

cruciate crural ligament The inferior extensor retinaculum of the foot (cruciate crural ligament, lower part of anterior annular ligament) is a Y-shaped band placed in front of the ankle-joint, the stem of the Y being attached laterally to the upper surface of the cal ...

, crosses from the lateral to the medial side of the anterior tibial vessels near the bend of the ankle, and is inserted into the base of the distal

phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particularly ...

of the great toe. 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.

Nerve supply

The extensor hallucis longus muscle is supplied by the

deep fibular nerve The deep fibular nerve (also known as deep peroneal nerve) begins at the bifurcation of the common fibular nerve between the fibula and upper part of the fibularis longus, passes infero-medially, deep to the extensor digitorum longus, to the anter ...

, a branch of

common fibular nerve The common fibular nerve (also known as the common peroneal nerve, external popliteal nerve, or lateral popliteal nerve) is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides at ...

, which includes L4, L5, and S1 spinal nerve roots.

Variations

Occasionally united at its origin with the

. The

extensor ossis metatarsi hallucis In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extendin ...

, 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.

Function

The extensor hallucis longus muscle extends the

big toe Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being '' digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being '' pl ...

, dorsiflects the foot, and also assists with foot eversion and inversion.

Additional Images

File:Gray440_color.png, Cross-section through middle of leg. (Extensores longi digitorum et hallucis labeled at upper left.) File:Slide1ABBAA.JPG, Dorsum of Foot. Deep dissection. File:Slide2ABBAA.JPG, Dorsum of Foot. Deep dissection. File:Slide2wewe.JPG, Ankle joint. Deep dissection. Medial view File:Slide2WIKI.JPG, Ankle joint. Deep dissection. Lateral view.

References

External links

* - "The Leg: Muscles"
University of Washington
{{Authority control Calf muscles Muscles of the lower limb