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 a p ...
. 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. The t ...
, 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; this ...
. Unlike the other extraocular muscles (recti and superior oblique), the inferior oblique muscle does ''not'' originate from the common tendinous ring (
annulus of Zinn
The common tendinous ring, also known as the annulus of Zinn, or annular tendon, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the common origin of the four recti muscles of the group of ex ...
).
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
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 human eye containing mainly collagen and some crucial elastic fiber. In humans, and som ...
l surface 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
lateral rectus
Lateral is a geometric term of location which may refer to:
Healthcare
* Lateral (anatomy), an anatomical direction
*Lateral cricoarytenoid muscle
*Lateral release (surgery), a surgical procedure on the side of a kneecap
Phonetics
*Lateral co ...
.
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
Action may refer to:
* Action (narrative), a literary mode
* Action fiction, a type of genre fiction
* Action game, a genre of video game
Film
* Action film, a genre of film
* ''Action'' (1921 film), a film by John Ford
* ''Action'' (1980 fi ...
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 § Vert ...
; 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.
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