The superior tarsal muscle (also known as Müller's muscle) is a smooth muscle adjoining the levator palpebrae superioris muscle that helps to raise the upper eyelid.

Structure

The superior tarsal muscle originates on the underside of levator palpebrae superioris and inserts on the superior tarsal plate of the eyelid.

Innervation

The superior tarsal muscle receives its innervation from the sympathetic nervous system on fibers carried along with the ophthalmic artery

Ophthalmic artery

The ophthalmic artery is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges...

 through the cavernous sinus

Cavernous sinus

The cavernous sinus , within the human head, is a large collection of thin-walled veins creating a cavity bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica.-Contents:...

. These postganglionic sympathetic fibers originate in the superior cervical ganglion

Superior cervical ganglion

The superior cervical ganglion , the largest of the cervical ganglia, is placed opposite the second and third cervical vertebræ. It contains neurons that supply sympathetic innervation to the face....

.

Actions

The superior tarsal muscle works with the levator palpebrae superioris to raise the upper eyelid.

Pathology

Damage to some elements of the sympathetic nervous system

Sympathetic nervous system

The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...

 can inhibit this muscle, causing a drooping eyelid (partial ptosis

Ptosis (eyelid)

Ptosis is a drooping of the upper or lower eyelid. The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to amblyopia...

). This is seen in Horner's syndrome

Horner's syndrome

Horner's syndrome is the combination of drooping of the eyelid and constriction of the pupil , sometimes accompanied by decreased sweating of the face on the same side; redness of the conjunctiva of the eye is often also present...

.

Eponym

The term "Müller's muscle" is sometimes used as a synonym.

However, the same term is also used for a portion of the ciliary muscle

Ciliary muscle

The ciliary muscle is a ring of striated smooth muscle in the eye's middle layer that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm's canal. It changes the shape of the lens within the eye not the size of the pupil which is...

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