A ring-like muscle in the eyelids and over the bony margin of the eye socket that closes the eye
Orbicularis oculi — the sphincter of the eyelids.
Anatomy · Muscles
Orbicularis oculi
The muscle of the blink and the genuine smile
Face · sphincter round the eye
A thin, flat, elliptical sphincter that lies in the eyelids and spreads out over the bony rim of the orbit. It closes the eyelids, gently in the blink and tightly in a squint, and it helps to pump tears through the lacrimal drainage system. It is supplied by the facial nerve, so a facial palsy leaves the eye unable to close.
How to spot them
- ▸A ring of fibres in the eyelids and round the orbital margin, in three parts: palpebral, orbital and lacrimal
- ▸Attached medially to the medial palpebral ligament and the bones beside the nose
- ▸Supplied by the temporal and zygomatic branches of the facial nerve
- ▸Its contraction produces the crow's feet at the outer corner of the eye
What to know
Its gentle inner part blinks, while the outer part screws the eyelids tightly shut
Orbicularis oculi — the palpebral and orbital parts.
A smile that involves this muscle and lifts the cheeks, crinkling the skin at the corners of the eyes, is described as genuine
Orbicularis oculi — the Duchenne smile, after Duchenne de Boulogne.
When the nerve that supplies it is paralysed the eye cannot be closed and the cornea dries out
Orbicularis oculi — a facial nerve palsy such as Bell's palsy.
A small part attached to the lacrimal bone helps to drain tears by squeezing the lacrimal sac
Orbicularis oculi — the lacrimal part, also called Horner's muscle.
Attached to a ligament running from the corner of the eye to the frontal process of the maxilla
Orbicularis oculi — the medial palpebral ligament.
It creates the lines radiating from the outer angle of the eye that deepen with age, and are often treated with botulinum toxin
Orbicularis oculi — crow's feet.
Key ideas
- The palpebral part blinks spontaneously without thought, about fifteen times a minute, spreading tears over the cornea; the orbital part is under voluntary control and gives the forced eye closure of a wince.
- Duchenne de Boulogne, who stimulated the faces of his subjects with electricity in the 1860s, argued that the outer part of this muscle is hard to contract at will, so that its involvement marks a spontaneous smile; later studies have shown that some people can contract it deliberately.
Quick-fire facts
- •Origin: the medial orbital margin (the frontal process of the maxilla and the nasal part of the frontal bone), the medial palpebral ligament and the lacrimal bone
- •Insertion: the skin around the margin of the orbit and the tarsal plates of the eyelids
- •Action: palpebral part gently closes the eyelids; orbital part tightly closes them; lacrimal part aids tear drainage
- •Nerve supply: temporal and zygomatic branches of the facial nerve
- •Blood supply: branches of the facial, superficial temporal, maxillary and ophthalmic arteries
- •Its antagonist, levator palpebrae superioris, is supplied by the oculomotor nerve
- •The Duchenne smile, named for the French neurologist Guillaume Duchenne de Boulogne, involves contraction of this muscle as well as of zygomaticus major
- •Bell's palsy causes weakness of the whole side of the face, including inability to close the eye
- •Bell's phenomenon is the upward roll of the eye when the eyelids are closed forcibly
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Sources
- TeachMeAnatomy — Orbicularis oculi