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The inferior rectus muscle, is shown in this superior view of the eye, along with its axis of rotation. The other muscle is the superior oblique muscle, which angles around the trochlea. The other muscle is the superior oblique muscle, which angles around the trochlea.
Thus, the medial rectus is the muscle closest to the nose. The superior and inferior recti do not pull straight back on the eye, because both muscles also pull slightly medially. This posterior medial angle causes the eye to roll with contraction of either the superior rectus muscle or the inferior rectus muscle.
The six muscles are four recti muscles – the lateral rectus, the medial rectus, the inferior rectus, and the superior rectus, and two oblique muscles the inferior oblique, and the superior oblique. The seventh muscle is the levator palpebrae superioris muscle. When the muscles exert different tensions, a torque is exerted on the globe that ...
Weakness of the inferior rectus muscle may strengthen the superior rectus muscle, causing it to be overreactive. [10] This may elevate the eye, and prevent its use in normal vision. [ 10 ] Treatment may involve eye surgery that weakens or repositions the superior rectus muscle, which generally has good outcomes.
In the primary position (eyes straight ahead), both of these groups contribute to vertical movement. Elevation is due to the action of the superior rectus and inferior oblique muscles, while depression is due to the action of the inferior rectus and superior oblique muscles. When the eye is abducted, the recti muscles are the prime vertical movers.
The main muscle for abduction is the lateral rectus, so although superior oblique contributes to a downwards and lateral eye movement, testing this motion would not be specific enough as inferior and lateral recti muscles would also be tested.
The oculomotor nerve includes axons of type GSE, general somatic efferent, which innervate skeletal muscle of the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique muscles. (Innervates all the extrinsic muscles except superior oblique and lateral rectus.)
The common tendinous ring spans the superior orbital fissure and can be described as having two parts – an inferior tendon which gives origin to the inferior rectus muscle, and to part of the lateral rectus muscle; and a superior tendon which gives origin to the superior rectus muscle, and to part of the medial and lateral recti muscles. [3]