Dominic Stone
The muscle that raises the eyelid is called the levator palpebrae superioris muscle. It is an extraocular muscle that originates from the periosteum immediately superior to the optic foramen and inserts onto the skin of the upper eyelid. The levator palpebrae superioris muscle is responsible for elevating and retracting the upper eyelid, allowing for an unhindered upward gaze. It also contributes to facial expressions by elevating the upper eyelid during feelings of fear, anger, and shock.
| Characteristics | Values |
|---|---|
| Muscle Name | Levator palpebrae superioris |
| Location | Originates from the inferior surface of the lesser wing of the sphenoid bone, just above the optic foramen |
| Type | Skeletal muscle |
| Function | Elevates and retracts the upper eyelid, allowing unhindered upward gaze |
| Innervation | Oculomotor nerve (CN III) |
| Blood Supply | Ophthalmic artery and its branches (lacrimal, supratrochlear, supraorbital, and muscular) |
| Drainage | Superior ophthalmic vein |
| Associated Structures | Whitnall ligament, levator aponeurosis, superior tarsal muscle (Müller's muscle) |
| Length | Approximately 40 mm |
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What You'll Learn
The levator palpebrae superioris muscle
Damage to the levator palpebrae superioris muscle or its innervation can result in ptosis, or drooping of the eyelid. This condition can also be caused by lesions in CN III or damage to the adjoining superior tarsal muscle and its sympathetic innervation. Therefore, the proper functioning of the levator palpebrae superioris muscle is crucial not only for eyelid movement but also for maintaining the normal position of the upper eyelid.
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Ptosis
The levator palpebrae superioris muscle, also known as the "elevating muscle of the upper eyelid", is responsible for raising the eyelids. This muscle originates from the inferior surface of the lesser wing of the sphenoid bone, just above the optic foramen. It transitions from muscle to tendon (aponeurosis) about 15 to 17 mm above the superior tarsal border. The levator palpebrae superioris muscle provides the majority of the elevation of the upper eyelid.
The condition can be congenital, where a person is born with ptosis, or acquired later in life. Congenital ptosis is caused by problems with the development of the levator muscle, the main muscle that lifts the eyelid. Acquired ptosis occurs when the levator muscle weakens or separates from the eyelid due to ageing, injury, or eye surgery. It can also be caused by damage to the nerves controlling the eyelid muscles or underlying medical problems.
The most obvious sign of ptosis is the drooping eyelid. Other symptoms include excessive eye rubbing, increased tearing, tiredness and achiness around the eyes, and children with ptosis may tip their heads back to see. Treatment options are available, and if ptosis is affecting vision, surgery is recommended to tighten the levator muscle or attach the eyelid to other muscles for support.
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The superior tarsal muscle
The STM receives its innervation from the sympathetic nervous system. Specifically, postganglionic sympathetic fibres originate in the superior cervical ganglion and travel through the internal carotid plexus, where they communicate with the oculomotor nerve as it passes through the cavernous sinus. These sympathetic fibres then continue to the superior division of the oculomotor nerve, where they enter the STM on its inferior aspect.
The role of the STM is not entirely clear, but it may function as an accessory muscle to the LPSM in raising the upper eyelid. The LPSM is a skeletal muscle, whereas the STM is a smooth muscle. This distinction is important as it can help clinicians distinguish between different causes of ptosis, which is the drooping of the eyelid. Damage to the STM or its innervation can lead to ptosis, and this can be differentiated from ptosis caused by LPSM paralysis, which typically presents with more pronounced eyelid drooping.
The STM has been the subject of morphological investigations, and different patterns of attachment to the STP have been identified. These patterns provide a basis for a proposed morphological classification of the STM. The histological analysis of cadaveric specimens has revealed a transitional area between the LPSM and the adjacent STM, highlighting the unique characteristics of these eyelid muscles.
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The Muller muscle
While the precise function of the Muller muscle is still a subject of debate, it is hypothesized to serve as an accessory upper eyelid retractor. Some researchers suggest that it plays a secondary role in maintaining eyelid tone, while others propose that it acts as a transmitter of the levator aponeurosis action or a stretch receptor for the LPS. Additionally, the Muller muscle may have a role in the pathogenesis of blepharospasm, with potential implications for the desensitization of mechanoreceptors in the treatment of this condition.
Surgical procedures involving the Muller muscle include Muller muscle-conjunctival resection, which has been employed in the treatment of blepharoptosis and phenylephrine test-negative blepharoptosis. Furthermore, Muller's muscle has been implicated in certain syndromes, such as Horner's syndrome, where sympathetic denervation can result in a 2- to 3-mm ptosis.
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The oculomotor nerve
CN III then exits the cranial cavity through the superior orbital fissure and divides into two main branches: the superior branch and the inferior branch. The superior branch is smaller, and it passes over the optic nerve to supply motor innervation to the superior rectus and levator palpebrae superioris muscles. The levator palpebrae superioris muscle is responsible for raising the upper eyelid, and the oculomotor nerve's innervation of this muscle helps in eyelid elevation.
The inferior branch, being the larger of the two, further divides into three branches. One branch supplies motor innervation to the medial rectus muscle, another to the inferior rectus muscle, and the third and longest branch runs forward to the inferior oblique muscle. Additionally, the inferior branch provides pre-ganglionic parasympathetic fibres to the ciliary ganglion, which ultimately innervates the sphincter pupillae and ciliary muscles.
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Frequently asked questions
The levator palpebrae superioris muscle, also known as the elevating muscle of the upper eyelid, is responsible for raising the eyelids.
The levator palpebrae superioris muscle is an extraocular muscle that facilitates movements of the eye by elevating and retracting the upper eyelid. It also allows for an unhindered upward gaze. This muscle is important for facial expressions as the elevation of the upper lid helps express feelings of fear, anger, and shock.
Damage to the levator palpebrae superioris muscle or its innervation can cause ptosis, which is the drooping of the eyelid. Lesions in CN III can lead to ptosis as the eyelid cannot oppose the force of gravity without stimulation from the oculomotor nerve.
