Extraocular Muscles... help

[Cowboy DO]

Ok I'm going nuts. What are the actions of the superior oblique and inferior oblique? My book contradicts my professors, and other sources also contradict each other. These ones for example, but there are others too:


http://www.meddean.luc.edu/Lumen/MedEd/GrossAnatomy/dissector/mml/so.htm

http://anatomy.uams.edu/HTMLpages/anatomyhtml/muscles_head&neck.html


Book (grants anatomy) says superior oblique depresses and ABDucts the eye. My notes from class say ADDucts the eye. Who do i believe?

a little help please.

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[Andrew_Doan]

Originally posted by Cowboy DO
Ok I'm going nuts. What are the actions of the superior oblique and inferior oblique? My book contradicts my professors, and other sources also contradict each other. These ones for example, but there are others too:

The primary action of the obliques are:

Superior obliques- intorsion
Inferior obliques- extorsion


The secondary action of the obliques are:

Superior obliques- depression
Inferior obliques- elevation

The tertiary action of the obliques are:

Superior obliques- ABduction
Inferior obliques- ABduction

 

[Redhawk]

This is taken from the Manual of Ocular Diagnosis and Therapy:

Concerning the SO muscle: "Contraction results in various combinations of vertical, horizontal and rotary movements, depending on the location of the eye horizontally. With a starting position of 39 degrees of aBduction, the only movement is INtorsion. With a starting position of 51 degrees of aDduction, the only movement is Depression. If the eye is in the primary position of straight-ahead gaze, the motion is combined INtorsion and Depression with minimum aBduction. ABduction is secondary to the muscle insertion, being posterior to the ocular rotation center when the eye is in primary position."

The two links that you provide don't seem to contradict....Both say that the SO muscle inserts posterior to the equator, meaning that if anything it will aBduct the eye.


Concerning the IO muscle: "Contraction results in various combinations of vertical, horizontal and rotary movements, depending on the location of the eye horizontally. With a starting position of 39 degrees of aBduction, the only movement is EXtorsion. If the starting position is 51 degrees of aDduction, the only movement is Elevation. Contraction of the muscle with the eye in primary position produces a combined EXtorsion and Elevation with minimum aBduction secondary to the insertion being posterior to the center of rotation."

 

[Cowboy DO]

Thanks thats what makes the most sense to me when I picture the muscles, the contradicting information though was two seconds from sending me right of the deep end. I still have to clarify this with my one professor though, maybe I miss understood him. Thanks again.

As far as the websites contradicting each other are concerned maybe I just dont understand when the one says that the "SO: Depresses eye in adduction. Medially rotates eye in abduction". shouldnt it depress in abduction?

 

[Andrew_Doan]

Originally posted by Cowboy DO

As far as the websites contradicting each other are concerned maybe I just dont understand when the one says that the "SO: Depresses eye in adduction. Medially rotates eye in abduction". shouldnt it depress in abduction?

Because of the muscle's insertion, it's primary, secondary, and tertiary actions are greatest in specific locations.

The SO can depress the eye when the eye is ADDUCTED by the other muscles. The IR depresses the eye in ABDUCTION.

In ABDUCTION, the SO can only intort (i.e. medially rotate) the eye, but has little role in DEPRESSION of the eye in this position.

 

[Cowboy DO]

gotcha, thanks.

 

[Redhawk]

Btw, if you're interested, here's a link to an ocular movement simulator:

http://cim.ucdavis.edu/EyeRelease/Interface/TopFrame.htm