Medial rectus muscle

Last revised by Assoc Prof Craig Hacking on 27 Dec 2021

The medial rectus muscle is one of the six extraocular muscles that control eye movements.

Medial rectus, along with the other rectus muscles, arises from the annulus of Zinn, the common tendinous ring at the apex of the orbit that surrounds the optic canal 1.

Medial rectus runs anteriorly on the medial surface of the eye and inserts into the medial surface of the sclera just posterior to the junction of cornea and sclera 2.

Branches of the ophthalmic artery, itself a branch of the internal carotid artery.

Innervated by the oculomotor nerve, which also supplies superior rectus, inferior rectus and inferior oblique muscles.

The action of the medial rectus is to adduct the eye (see figure 1) 1. Unlike most of the other extraocular muscles, it has no significant contribution to movement in the other ocular axes.

Simultaneous action of the medial rectus muscles of both eyes causes ocular convergence, which is necessary to allow near-field focus, such as when reading.

Rectus comes from the Latin rectos, meaning straight 1.

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Cases and figures

  • Figure 1: extra-ocular muscles
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  • Figure 2: extra-ocular muscles
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  • Figure 3: anatomy of the extraocular muscles
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  • Figure 4: anatomy of the extraocular muscles
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  • Figure 5: extraocular muscle movement
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  • Figure 6: innervation of the medial and lateral recti muscles (Gray's illustration)
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  • Figure 7: origins of the extraocular muscles (Gray's illustration)
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  • Case 1: labeled 15
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