CorpusHuman Anatomy
MuscularMuscle

Orbicularis oculi

Musculus orbicularis oculi

Also known as: eyelid sphincter, blink muscle

The sphincter of the eyelids, encircling the orbit. Its palpebral part closes the eye gently (blinking) and its orbital part screws the eye shut.

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Overview

Orbicularis oculi has three parts. The thick orbital part encircles the orbital margin and produces forced, tight closure of the eye ("screwing up" the eye against glare, dust or a blow), wrinkling the surrounding skin into crow's-feet. The thin palpebral part lies within the eyelids, anterior to the tarsal plates. It closes the lids gently, as in blinking and sleep. The lacrimal part (Horner's muscle) passes behind the lacrimal sac. It draws the lids and puncta medially and may dilate the sac, pumping tears into the nasolacrimal duct.

Blinking spreads the tear film across the cornea every few seconds. The corneal (blink) reflex has a trigeminal afferent limb (V1) and a facial efferent limb (VII) acting on this muscle. Levator palpebrae superioris (CN III) is its antagonist.

Location

Around the orbit and within the eyelids.

Parts & subdivisions

  1. Orbital part
    Encircles the orbital margin. Produces forced closure.
  2. Palpebral part
    In the eyelids. Produces gentle closure and blinking.
  3. Lacrimal part
    Behind the lacrimal sac. Aids tear drainage.

Anatomy

Origin

Nasal part of the frontal bone, frontal process of the maxilla, medial palpebral ligament and lacrimal bone (posterior lacrimal crest).

Insertion

Skin around the orbital margin, the lateral palpebral raphe and the superior and inferior tarsal plates.

Action

Closes the eyelids. The palpebral part closes them gently, the orbital part closes them tightly, and the lacrimal part assists tear drainage.

Innervation

Facial nerve (CN VII), temporal and zygomatic branches.

Nerve roots

Cranial nerve VII; no spinal roots

Arterial supply

Facial artery (angular branch), superficial temporal artery, and ophthalmic artery branches (supraorbital, lacrimal, palpebral).

Relations

Antagonist: levator palpebrae superioris (CN III) and the superior tarsal (Müller) muscle (sympathetic).

Function

  • Closes the eyelids (blinking, forced closure)
  • Spreads tears and helps drain them
  • Protects the eye

Clinical significance

Exposure keratitis in facial palsy

Paralysis of orbicularis oculi stops the eye from closing (lagophthalmos), and the lower lid sags outward (ectropion), so tears spill onto the cheek (epiphora). The cornea dries and ulcerates unless it is protected with lubricants, taping or tarsorrhaphy.

Blepharospasm

Focal dystonia with involuntary forceful closure of the eyelids. Treated with botulinum toxin.

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.