The inferior oblique muscle or obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

. The inferior oblique is one of the

extraocular muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the othe ...

, and is attached to the

maxillary bone The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

(origin) and the posterior, inferior, lateral surface of the eye (insertion). The inferior oblique is innervated by the inferior branch of the oculomotor nerve.

Structure

The inferior oblique arises from the orbital surface of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

, lateral to the lacrimal groove. Unlike the other extraocular muscles (recti and superior oblique), the inferior oblique muscle does ''not'' originate from the common tendinous ring ( annulus of Zinn). Passing lateralward, backward, and upward, between the

inferior rectus Inferior may refer to: * Inferiority complex * An anatomical term of location * Inferior angle of the scapula, in the human skeleton * ''Inferior'' (book), by Angela Saini * ''The Inferior'', a 2007 novel by Peadar Ó Guilín See also *Junior (di ...

and the floor of the orbit, and just underneath the lateral rectus muscle, the inferior oblique inserts onto the scleral surface between the

and lateral rectus. In humans, the muscle is about 35 mm long.

Innervation

The inferior oblique is innervated by the inferior division of the oculomotor nerve (cranial nerve III).

Function

Its actions are extorsion, elevation and abduction of the eye. Primary action is extorsion (external rotation); secondary action is

elevation The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Ver ...

; tertiary action is abduction (i.e. it extorts the eye and moves it upward and outwards). The field of maximal inferior oblique elevation is in the adducted position. The inferior oblique muscle is the only muscle that is capable of elevating the eye when it is in a fully adducted position. Torsional eye movement with partial heterochromia

Torsional eye movement with partial heterochromia

Clinical significance

While commonly affected by palsies of the inferior division of the oculomotor nerve, isolated palsies of the inferior oblique (without affecting other functions of the oculomotor nerve) are quite rare. "Overaction" of the inferior oblique muscle is a commonly observed component of childhood

strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...

, particularly infantile

esotropia Esotropia is a form of strabismus in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. It is the opposite of exotropia and usual ...

and

exotropia Exotropia is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia and usually involves more severe axis deviation than exophoria. People with exotropia often experience crossed diplopia. Intermittent exotrop ...

. Because true hyperinnervation is not usually present, this phenomenon is better termed "elevation in adduction". Surgical procedures of the inferior oblique include: loosening (also known as recession see Strabismus surgery), myectomy, marginal myotomy, and denervation and extirpation. It is also encountered and identified in lower lid blepharoplasty surgeries.

Additional images

File:Gray890.png, Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure. File:Slide13uu.JPG, Inferior oblique muscle File:Slide8ababa.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection. File:Slide9abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection.

References

External links

* * ()
Image at childrenshospital.org
{{Authority control Muscles of the head and neck Human eye anatomy