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The extraocular muscles and their innervation. The medial rectus muscle has been sectioned and retracted in this drawing of the right eye to show the position of the extraocular muscles. The course of cranial nerves (CNs) III (oculomotor, superior and inferior divisions), IV (trochlear), and VI (abducens) are shown as they enter the orbit through the superior orbital fissure to innervate the extraocular muscles. Note that CN IV enters the orbit outside of the annulus of Zinn. The action of each of the extraocular muscles is a logical consequence of its insertion on the globe and direction of action. The medial and lateral rectus muscles insert anterior to the equator of the globe and pull directly posteriorly, rotating the globe in the horizontal plane. Similarly, the superior and inferior rectus muscles move the eye in the vertical plane. However, the superior and inferior rectus muscles insert at a slight angle relative to Source: Ocular Motility Disorders: Extraocular Muscles and the Neuromuscular Junction, Practical Neuroophthalmology the visual axis, so they also cause some torsion and adduction of the globe (inset). The oblique muscles insert posterior to the equator and pull Citation: JJ.oblique Practicaldepresses Neuroophthalmology; 2013oblique Available at: http://mhmedical.com/ Accessed: April anteromedially (inset).Martin Thus,TJ, theCorbett superior and the inferior elevates. The torsional forces generated by30, the2017 oblique muscles Copyright © 2017 McGraw-Hill Education. All rights reserved should be evident from this diagram.