They originate either from the orbit or a tendinous

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They originate either from theorbit or a tendinous ring that surrounds the optic nerve and insert on the eyeball.Thereare four “rectus” (straight) muscles and two “oblique” muscles.Table 9.3.Extrinsic Eye MusclesNameOriginInsertionInnervationAction210© 2011 Shirley J. Wright, Ph.D.
SuperiorRectusAnnulus ofZinn at theorbital apexSuperiorsurface of theeyeballOculomotornerve (III)Moves the eye sothat the cornea isdirected upwards(elevation) andmedially adductedInferior RectusAnnulus ofZinn at theorbital apexInferior surfaceof the eyeballOculomotornerve (III)Moves the eye sothat the cornea isdirected downwards(depression)Medial RectusMedialtendinousring withinorbit(Annulus ofZinn at theorbital apex)Medial surfaceof the eyeballOculomotornerve (III)Moves the eye sothat the cornea isdirected medially(adducted)Lateral RectusLateraltendinousring withorbit(Annulus ofZinn at theorbital apex)Lateral surfaceof the eyeballAbducensNerve (VI)Moves the eye sothat the cornea isdirected laterally(abducted)SuperiorObliqueBody ofsphenoidabovetendinousPosterosuperiorsurface of theeyeball. Usesthe trochlear asTrochlearNerve (IV)Depresses theposterior aspect ofthe eye, depressingthe cornea211© 2011 Shirley J. Wright, Ph.D.
ring(Annulus ofZinn at theorbital apex,medial tooptic)a pulleyInferior ObliqueOrbitalsurface ofmaxilla,behindorbitalmargin;lateral to thelacrimalInferior surfaceof the eyeballOculomotornerve (III)Depresses theposterior aspect ofthe eye, elevatingthe corneaCheck:Primal Pictures→ Systemic Anatomy - Systemic Edition → Special senses →Chapter contents → Extrinsic eye muscles.Wall of Eyeball.Thewall of the eyeball is composed of three concentric membranes ortunics lying one on top of the other:an outer fibrous layer (tunica fibrosa), a middlevascular layer (tunica vasculosa), and an inner retinal or neural layer (tunica interna).Tunica fibrosa:outer fibrous layer composed of an anteriorcorneaand a posteriorsclera(white of eye).Tunica vasculosa:middle vascular layer also calleduvea.Has three regions:choroidposteriorly and theciliary body(supports lens and contains a ciliarymuscle that focuses the lens) andiris(colored part of eye that controls the diameterof the pupil) anteriorly.Tunica interna:consists of theretinawhich contains light receptors.Themaculaluteais a yellow spot that is the point of the clearest vision.At the center of themacula lutea is a tiny pit called thefovea centraliswhich is the spot where vision ismost accurate (e.g., images are most finely detailed).The axons of the ganglioncells of the retina form the optic nerve, and the optic disc is the spot where the opticnerve leaves the rear of the eyeball.Optical Components.The optical components of the eye are transparent structuresthat transmit light to the retina.212© 2011 Shirley J. Wright, Ph.D.
Aqueous humor.Clear serous fluid secreted by the ciliary body into a space calledtheposterior chamber(located between the iris and lens).

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Human Anatomy, Shirley J Wright

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