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Extra-ocular muscles

Other Terms: Eye muscles, Extraocular muscles, Pre-otic somite muscles, Extra-ocular muscles, Extra-ocular muscle group, Extrinsic muscles of eyeball, Set of extrinsic muscles of eyeball, Extra-ocular muscles set, Muscles extra-oculaires, Musculi externa bulbi oculi

Description

The extra-ocular, or extrinsic eye, muscles are a series of small muscles that arise from the pre-otic somites in the developing head. Associated with these somites are the three ventral motor cranial nerves (III or the oculomotor, IV or the trochlear, and VI or the abducens) rostral to the developing ear. The seven extra-ocular muscles encircle the eye within the orbit. Six of the seven muscles attach to the sclera of the eye and produce the complete range of eye movements. The seventh muscle moves the upper eyelid out of the visual pathway. The six muscles of the eyeball are an incredibly stable muscle group over the long history of vertebrate evolution. Across the entire range of vertebrate animals, from fish to mammals, the six extra-ocular muscles show little variation. These intricately controlled muscles have some of the highest neuron to muscle fiber ratios in the body, with motor units consisting of approximately ten muscle fibers. The levator palpebrae superioris, the only member of the group that does not attach to the eyeball, develops by splitting away from the superior rectus muscle and attaching to the tarsal plate of the eyelid in those animals that develop an upper lid over the eye.

Muscles Included

Superior rectus, Inferior rectus, Lateral rectus, Medial rectus, Superir oblique, Inferior oblique, and the Levator palpebrae superiores

French

Muscles extra-oculaires

Latin

Musculi externa bulbi oculi

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