|Muscle||Innervation||Origin||Insertion||Primary function||Secondary function||Tertiary function|
|Superior rectus||Superior branch of oculomotor nerve||Annulus of Zinn||eye (anterior, superior surface)||Elevation||Intorsion||Adduction|
|Inferior rectus||Inferior branch of oculomotor nerve||Annulus of Zinn||eye (anterior, inferior surface)||Depression||Extorsion||Adduction|
|Lateral rectus||Abducens nerve||Annulus of Zinn||eye (anterior, lateral surface)||Abduction|
|Medial rectus||Inferior branch of oculomotor nerve||Annulus of Zinn||eye (anterior, medial surface)||Adduction|
|Superior oblique||Trochlear nerve||Annulus of Zinn||eye (posterior, superior, lateral surface)||Intorsion||Depression||Abduction|
|Inferior oblique||Inferior branch of oculomotor nerve||Maxillary bone||eye (posterior, inferior, lateral surface)||Extorsion||Elevation||Abduction|
|Medial (towards nose)||Lateral (towards temple)|
| Elevation, adduction:|
| Elevation, abduction:|
| Depression, adduction:|
| Depression, abduction:|
In an eye examination, the inability of the patient to move the eye in the specified direction can indicate a problem with the associated muscle, and the nerve associated with that muscle.
There are two main kinds of movement: conjugate movement (the eyes move in the same direction) and disjunctive (opposite directions). The former is typicsl when shifting gaze right or left, the latter is convergence of the two eyes on a near object. Disjunction can be performed voluntarily, but is usually triggered by the nearness of the target object. A "see-saw" movement, namely, one eye looks up and the other down, is possible, but not voluntarily; this effect is brought on by putting a prism in front of one eye, and the relevant image is apparently displaced. However, to avoid double vision from noncorrsponding points from, the eye with the prism must move up or down, following the image passing through the prism. Likewise torsion (rolling) on the anteroposterior axis (from the front to the back) can occur naturally, as when one tips his head to one shoulder, the torsion, in the opposite direction, keeps the image vertical.
The muscles show little inertia, so a shutdown of one muscle is not due to checking of the antagonist, so the motion is not ballistic.
Four of these then course forward through the orbit and insert onto the globe on its anterior half (i.e., in front of the eye's equator). These muscles are named after their straight paths, and are called the four rectus muscles, or four recti.
(Note that lateral and medial are relative to the subject, with lateral toward the side and medial toward the midline, thus the medial rectus is the muscle closest to the nose).
The superior and inferior recti are not strictly vertical. The oblique pull of the obliques causes a rolling opposite each other. Although bearing mutual strict antagonism, the superior and inferior rectus team up with the inferior and superior oblique to move the eye up or down, respectively. The extent of rolling in the recti is less than the oblique, and opposite from it.
Another way to remember which nerves innervate which muscles is to understand the meaning behind all of the Latin words.
Research findings from Bogazici University, Biomedical Engineering Institute update understanding of life sciences.(Report)
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