Tibialis anterior muscle

Tibialis anterior muscle
Lateral aspect of right leg.
Tibialis anterior
Latin	musculus tibialis anterior
Gray's	subject #129 480
Origin	body of tibia
Insertion	medial cuneiform and first metatarsal bones of the foot
Artery	anterior tibial artery
Nerve	Deep Fibular (peroneal) nerve
Actions	Dorsiflexion and Inversion of the foot
Antagonist	Fibularis longus, Gastrocnemius, Soleus, Plantaris, Tibialis posterior

In human anatomy, the tibialis anterior is a muscle that originates in the upper two-thirds of the lateral surface of the tibia and inserts into the medial cuneiform and first metatarsal bones of the foot. Its acts to dorsiflex and invert the foot. This muscle is mostly located near the shin.

It is situated on the lateral side of the tibia; it is thick and fleshy above, tendinous below. The tibialis anterior overlaps the anterior tibial vessels and deep peroneal nerve in the upper part of the leg.

Function

The tibialis anterior muscle is the most medial muscle of the anterior compartment of the leg. The tibialis anterior is responsible for dorsiflexing and inverting the foot. The muscle has two origins, one being the lateral tibial condyle and the other being the upper lateral surface of the tibia, and inserts on the medial surface of the medial cuneiform and adjoining part of base of the first metatarsal of the foot allowing the toe to be pulled up and held in a locked position. It also allows for the ankle to be inverted giving the ankle horizontal movement allowing for some cushion if the ankle were to be rolled. It is innervated by the deep fibular nerve and acts as both an antagonist and a synergist of the tibialis posterior. However, the most accurate antogonist of the tibialis anterior is the peroneus longus. The tibialis anterior aides in the activities of walking, running, hiking, kicking a ball, or any activity that requires moving the leg or keeping the leg vertical. It functions to stabilize the ankle as the foot hits the ground during the contact phase of walking (eccentric contraction) and acts later to pull the foot clear of the ground during the swing phase (concentric contraction). It also functions to 'lock' the ankle, as in toe-kicking a ball, when held in an isometric contraction.

Antagonists are plantar-flexors of the posterior compartment such as soleus and gastrocnemius.

Essentially, the movements of tibialis anterior are dorsiflexion and inversion of the ankle. However, actions of tibialis anterior are dependent on whether the foot is weight bearing or not (closed or open kinetic chain). When the foot is on the ground the muscle helps to balance the leg and talus on the other tarsal bones so that the leg is kept vertical even when walking on uneven ground.

Origin and insertion

It arises from the lateral condyle and upper half or two-thirds of the lateral surface of the body of the tibia; from the adjoining part of the interosseous membrane; from the deep surface of the fascia; and from the intermuscular septum between it and the extensor digitorum longus.

The fibers of this fusiform muscle are relatively parallel to the plane on insertion, ending in a tendon, apparent on the anteriomedial dorsal aspect of the foot close to the ankle.

After passing through the most medial compartments of the transverse and cruciate crural ligaments, it is inserted into the medial and under surface of the medial cuneiform bone and the base of the first metatarsal bone.

Variations

A deep portion of the muscle is rarely inserted into the talus, or a tendinous slip may pass to the head of the first metatarsal bone or the base of the first phalanx of the great toe.

The tibiofascialis anterior, a small muscle from the lower part of the tibia to the transverse or cruciate crural ligaments or deep fascia.^{[clarification needed]}

Additional images

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  Bones of the right leg. Anterior surface.

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  Bones of the right foot. Plantar surface.

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  Anatomical terms of motion

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  Cross-section through middle of leg.

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  The sheaths of the tendons around the ankle. Medial aspect.

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  The sheaths of the tendons around the ankle. Lateral aspect.

External links

• LUC tiba

• SUNY Labs 15:st-0415

• http://www.wheelessonline.com/ortho/tibialis_anterior

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.