Retraction of eyelids?

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Lothric

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Hi,

I've learnt that retraction and protraction are used to describe adduction and abduction, respectively.

However, when reading about the eyelids, FA says that "sympathetic fibers innervate smooth muscle of eyelids (minor retractors)".

The muscle they're referring to is m. tarsalis superior. This muscle keeps the eye open, and is thus abducting the eyelids. Isn't this a protraction then?

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Protraction and Retraction are terms used to describe movement of the eyelid. Protraction for closing it, retraction for opening it. See below for more detail about innervation and primary muscles.
Adduction and abduction are terms used to describe eye movement. Adduction describing movement of eye towards the nose, abduction for movement of the eye towards temporal. Ie. adduction of eye is due to mainly medial rectus, abduction of eye is due to lateral rectus.

Nerve supply of the eyelids - EyeWiki
The facial nerve (CNVII) innervates the obicularis oculi, frontalis, procerus, and corrugator supercilii muscles, and supports eyelid protraction. The temporal and zygomatic branches of the facial nerve supply the obicularis oculi, the main eyelid protractor. The facial nerve also supplies the corrugator supercilii and the procerus, both of which secondarily contribute to upper eyelid protraction.

The oculomotor nerve (CNIII) innervates the main upper eyelid retractor, the levator palpebrae superiorus, via its superior branch. Sympathetic fibers contribute to upper eyelid retraction by innervation of the superior tarsal muscle, also known as Müller's muscle. Sympathetic fibers also innervate the inferior tarsal muscle, contributing to lower lid retraction.

Hope this helps!
 
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