Levator palpebrae superioris

The levator palpebrae superioris is a striated muscle of the orbit. It originates around the optic canal with the muscles of the eyeball, but does not insert onto the eyeball. It runs rostrally, dorsal to the other muscles, and passes beyond the bulb to insert into the superior eyelid.

Configuration: Orbital striated muscle

Origin: Apex of the orbit, surrounding the optic canal

Insertion: Superior eyelid

Relations: Dorsal to the eyeball, dorsal to the other muscles of the eyeball, crossing the orbital septum, attaching between the superior tarsus and the orbicularis oculi muscle.

Action: Elevation of the superior eyelid

Vascularization: Muscular branches of the external ophthalmic artery, ophthalmic plexus

Innervation: Dorsal branch of the oculomotor nerve

Description:

The levator palpebrae superioris is one of the striated muscles of the orbit.

It is the only muscle of the orbit that does not attach to the eyeball. It arises at the apex of the orbit near the optic canal, attaching to the periorbita, along with the other muscles of the orbit. The levator palpebrae superioris runs rostrally towards the eyeball, located dorsally to the other muscles. It gradually widens and becomes a broad aponeurosis that inserts into the eyelid. It passes over the eyeball and emerges from the orbit, crossing the orbital septum and inserting between the superior tarsus and the orbicularis oculi muscle.

Contraction of this muscle raises the superior eyelid and opens the palpebral fissure. The superior tarsal muscle also participates in these actions, but the presence of the levator palpebrae superioris explains the difference in mobility between the superior and inferior eyelids.

This muscle is vascularized by the muscular branches of the external ophthalmic artery. It is drained by veins forming part of the ophthalmic plexus.

It is innervated by the dorsal branch of the oculomotor nerve. This nerve enters the orbit through the orbital fissure and reaches the ventral aspect of the muscle.

Variations:

In rabbits, the main fascicle of this muscle has a conformation similar to that of other species, but a distinct muscle fascicle detaches from it and inserts at the base of the third eyelid, contributing to its retraction.

In humans, the insertion aponeurosis of this muscle is divided into two blades. A superficial blade that inserts into the subcutaneous tissue of the eyelid, and a deep blade that attaches to the anterior surface of the tarsus.