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The extraocular muscles, or extrinsic ocular muscles, are the seven extrinsic muscles of the eye in humans and other animals. [1] Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye. The other muscle, the levator palpebrae superioris, controls eyelid elevation.
An eyelid (/ ˈ aɪ. l ɪ d / EYE-lid) is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily.
The orbicularis oculi is a muscle in the face that closes the eyelids.It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament.
Damage to this muscle or its innervation can cause ptosis, which is drooping of the eyelid. [4] [5] Lesions in CN III can cause ptosis, [5] because without stimulation from the oculomotor nerve the levator palpebrae cannot oppose the force of gravity, and the eyelid droops.
An eyelid is a thin fold of skin that covers and protects the eye. The levator palpebrae superioris muscle helps in the movement of eyelid. The human eyelid features a row of eyelashes along the eyelid margin, which helps in protection of the eye from dust and foreign debris. The main function of eyelid is to keep the cornea moist and clean.
The superior tarsal muscle receives its innervation from the sympathetic nervous system.Postganglionic sympathetic fibers originate in the superior cervical ganglion, and travel via the internal carotid plexus, where small branches communicate with the oculomotor nerve as it passes through the cavernous sinus. [1]
Intrinsic ocular muscles [1] or intraocular muscles [2] are muscles of the inside of the eye structure. The intraocular muscles are responsible for the protraction and retraction of the eyelids and reaction to light and pupil accommodation . [ 2 ]
The seventh muscle is the levator palpebrae superioris muscle. When the muscles exert different tensions, a torque is exerted on the globe that causes it to turn, in almost pure rotation, with only about one millimeter of translation. [7] Thus, the eye can be considered as undergoing rotations about a single point in the centre of the eye.