Levator palpebrae superioris muscle

The levator palpebrae superioris (or levator muscle of upper eyelid) is the muscle in the orbit that elevates the superior (upper) eyelid.

Structure
The levator palpebrae superioris originates on the lesser wing of the sphenoid bone, just above the optic foramen. It broadens and becomes the levator aponeurosis. This portion inserts on the skin of the upper eyelid, as well as the superior tarsal plate. It is a skeletal muscle. The superior tarsal muscle, a smooth muscle, is attached to the levator palpebrae superioris, and inserts on the superior tarsal plate as well.

Innervation
As with most of the muscles of the orbit, it is innervated by the superior division of the oculomotor nerve (Cranial Nerve III). This is why when one looks upward, the eyelid tends to move up with it. An adjoining smooth muscle, the superior tarsal muscle, is sympathetically innervated and is occasionally considered to be part of the levator palpebrae superioris.

Actions
The levator palpebrae superioris muscle elevates and retracts the upper eyelid.

Pathology
Damage to this muscle, or its innervation, can cause ptosis, the drooping of the eyelid. Ptosis can also be caused by damage to the adjoining superior tarsal muscle, or its sympathetic innervation. Such damage to the sympathetic supply occurs in Horner's syndrome, and presents as a partial ptosis.