Lateral rectus muscle

Musculus rectus lateralis bulbi oculi

  • Latin synonym: Musculus rectus lateralis
  • Related terms: Lateral rectus

Definition

Origin: Annulus of Zinn at the orbital apex

Insertion: 7 mm temporal to the corneal limbus

Nerve: Abducens nerve

Action: Abducts the eyeball

Description:
The lateral rectus muscle is a muscle in the orbit. It is one of six extraocular muscles that control the movements of the eye (abduction in this case) and the only muscle innervated by the abducens nerve, cranial nerve VI. Its function is to bring the pupil away from the midline of the body. It is tested clinically by asking the patient to look laterally.

The four Recti arise from a fibrous ring (annulus tendineus communis) which surrounds the upper, medial, and lower margins of the optic foramen and encircles the optic nerve. The ring is completed by a tendinous bridge prolonged over the lower and medial part of the superior orbital fissure and attached to a tubercle on the margin of the great wing of the sphenoid, bounding the fissure. Two specialized parts of this fibrous ring may be made out: a lower, the ligament or tendon of Zinn, which gives origin to the Rectus inferior, part of the Rectus internus, and the lower head of origin of the Rectus lateralis; and an upper, which gives origin to the Rectus superior, the rest of the Rectus medialis, and the upper head of the Rectus lateralis. This upper band is sometimes termed the superior tendon of Lockwood. Each muscle passes forward in the position implied by its name, to be inserted by a tendinous expansion into the sclera, about 6 mm. from the margin of the cornea. Between the two heads of the Rectus lateralis is a narrow interval, through which pass the two divisions of the oculomotor nerve, the nasociliary nerve, the abducent nerve, and the ophthalmic vein. Although these muscles present a common origin and are inserted in a similar manner into the sclera, there are certain differences to be observed in them as regards their length and breadth. The Rectus medialis is the broadest, the Rectus lateralis the longest, and the Rectus superior the thinnest and narrowest.

This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).

Comparative anatomy in animals

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