The superior tarsal muscle is a

smooth muscle Smooth muscle is an involuntary non- striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit ...

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.

Nerve supply

The superior tarsal muscle receives its innervation from the

sympathetic nervous system The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...

. Postganglionic sympathetic fibers originate in the superior cervical ganglion, and travel via the internal carotid plexus, where small branches communicate with the

oculomotor nerve The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of ...

as it passes through the

cavernous sinus The cavernous sinus within the human head is one of the dural venous sinuses creating a cavity called the lateral sellar compartment bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica. Structure The cave ...

. The sympathetic fibres continue to the superior division of the

, where they enter the superior tarsal muscle on its inferior aspect.

Function

Its role is not fully clear, but may be an accessory muscle to raise the upper eyelid.

Clinical significance

Damage to some elements of the

can inhibit this muscle, causing a drooping eyelid (partial ptosis). This is seen in

Horner's syndrome Horner's syndrome, also known as oculosympathetic paresis, is a combination of symptoms that arises when a group of nerves known as the sympathetic trunk is damaged. The signs and symptoms occur on the same side (ipsilateral) as it is a lesion ...

. The ptosis seen in Horner's syndrome is of a lesser degree than is seen with an oculomotor nerve palsy.

History

The muscle derives its name , typically used for drying. The term ''Müller's muscle'' is sometimes used as a synonym. However, the same term is also used for the circular fibres of the ciliary muscle, and also for the orbitalis muscle that covers the inferior orbital fissure. Given the possible confusion, the use of the term ''Müller's muscle'' should be discouraged unless the context removes any ambiguity.

Structure

Nerve supply

Function

Clinical significance

History

See also

References

Further reading