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 (also known as orbital revolution) 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 ...

. The inferior oblique is one of the

extraocular muscles The extraocular muscles, or extrinsic ocular muscles, are the seven extrinsic muscles of the eye in human eye, humans and other animals. Six of the extraocular muscles, the four recti muscles, and the superior oblique muscle, superior and inferior ...

, and is attached to the maxillary bone (origin) and the posterior, inferior, lateral surface of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

(insertion). The inferior oblique is innervated by the inferior branch of the

oculomotor nerve The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements o ...

Structure

The inferior oblique arises from the orbital surface of the

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

, lateral to the

lacrimal groove On the nasal surface of the body of the maxilla, in front of the opening of the sinus is a deep groove, the lacrimal groove (or lacrimal sulcus), which is converted into the nasolacrimal canal, by the lacrimal bone and inferior nasal concha; thi ...

. 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 and the floor of the orbit, and just underneath the lateral rectus muscle, the inferior oblique inserts onto the

sclera The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective outer layer of the eye containing mainly collagen and some crucial elastic fiber. In the development of t ...

l surface between the inferior rectus and lateral rectus. In humans, the muscle is about 35 mm long.

Innervation

The inferior oblique is innervated by the inferior division of the

(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 (geography), ''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 equipotenti ...

; 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 an eye disorder in which the eyes do not properly align with each other when looking at an object. The eye that is pointed at 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 turn 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 us ...

and exotropia. 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 Strabismus surgery (also: ''extraocular muscle surgery'', ''eye muscle surgery'', or ''eye alignment surgery'') is surgery on the extraocular muscles to correct strabismus, the misalignment of the human eye, eyes. Strabismus surgery is a one-day ...

), 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.

References

External links

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