Inferior oblique muscle

Inferior oblique
Rectus muscles: 2 = superior, 3 = inferior, 4 = medial, 5 = lateral Oblique muscles: 6 = superior, 8 = inferior Other muscle: 9 = levator palpebrae superioris Other structures: 1 = Annulus of Zinn, 7 = Trochlea, 10 = Superior tarsus, 11 = Sclera, 12 = Optic nerve
Sagittal section of right orbital cavity.
Latin	musculus obliquus inferior bulbi
Gray's	subject #227 1023
Origin	orbital surface of the maxilla, lateral to the lacrimal groove
Insertion	laterally onto the eyeball, deep to the lateral rectus, by a short flat tendon
Artery	ophthalmic artery
Nerve	oculomotor nerve
Actions	extorsion, elevation, abduction

The Obliquus oculi inferior (inferior oblique) is a thin, narrow muscle placed near the anterior margin of the floor of the orbit.

Action

Its actions are lateral rotation, elevation and abduction of the eye.

Primary action is extorsion; secondary action is elevation; 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.^[1]

Path

The inferior oblique arises from the orbital surface of the maxilla, lateral to the lacrimal groove.

Passing lateralward, backward, and upward, between the inferior rectus and the floor of the orbit, the inferior oblique inserts onto the scleral surface between the inferior rectus and lateral rectus.

The origin of the inferior oblique muscle is not on the common tendinous ring (annulus of Zinn).

Innervation

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

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, particularly infantile esotropia and exotropia. Because true hyperinnervation is not usually present, this phenomenon is better termed "elevation in adduction".^[2]

Surgical procedures of the inferior oblique include: loosening (also known as recession see Strabismus_surgery), myectomy, marginal myotomy, and denervation and extirpation.

Additional images

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  Eye movement of lateral rectus muscle, superior view

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  Eye movement of medial rectus muscle, superior view

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  Eye movement of inferior rectus muscle, superior view

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  Eye movement of superior rectus muscle, superior view

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  Eye movement of superior oblique muscle, superior view

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  Eye movement of inferior oblique muscle, superior view

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  Anterior view

credit: Patrick J. Lynch

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  Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.

External links

• LUC io
• -133824433 at GPnotebook
• SUNY Figs 29:01-08
• inferior+oblique+muscle at eMedicine Dictionary
• lesson3 at The Anatomy Lesson by Wesley Norman (Georgetown University) (orbit5)
• Image at childrenshospital.org

References

1. ^ http://cim.ucdavis.edu/Eyes/eyeText.htm
2. ^ Kushner BJ (2006). "Multiple mechanisms of extraocular muscle 'overaction'". Arch Ophthalmol 124 (5): 680–8. doi:10.1001/archopht.124.5.680. PMID 16682590. 

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.