Flat, elliptical sphincter of facial expression surrounding the orbital opening, within the eyelids. Supplied by facial nerve (CN VII) — nerve of 2nd pharyngeal arch. Three parts: orbital, palpebral, lacrimal.

Orbital Part

• Origin: Medial palpebral ligament, frontal process of maxilla, nasal part of frontal bone
• Course: Complete elliptical loops on/around orbital margin, no interruption, return to origin
• Action: Closes eyelids tightly and forcefully; protects eye from light, wind, dust, rain; voluntary tight closure (winking, screwing eyes)

Palpebral Part

• Origin: Medial palpebral ligament
• Course: Sweeps laterally over upper + lower eyelids → lateral palpebral ligament (lateral palpebral raphe); small group along lid margins = ciliary bundle (muscle of Riolan)
• Action: Closes eyelids gently — blinking, sleep

Lacrimal Part

• Origin: Posterior lacrimal crest + lacrimal fascia (behind lacrimal sac; forms sheath around sac)
• Course: Passes laterally in front of tarsal plates → lateral palpebral raphe
• Action: Dilates lacrimal sac by traction on lacrimal fascia → draws tears from lacus lacrimalis into sac via puncta + canaliculi = “lacrimal pump”; supports lower eyelid

Nerve Supply

• Temporal branch of facial nerve (CN VII) — frontalis, auricular muscles, orbicularis oculi
• Zygomatic branch — also supplies orbicularis oculi

Applied Anatomy

Bell’s Palsy — LMN lesion of facial nerve (at/near stylomastoid foramen) → orbicularis oculi paralysis:

• Widening of palpebral fissure + inability to close eye (lagophthalmos)
• Tears flowing down face (epiphora) — lacrimal pump failure + lower lid sag (ectropion)
• Loss of horizontal forehead wrinkles (occipitofrontalis paralysis)

In UMN (supranuclear) lesions: upper face (including orbicularis oculi) escapes paralysis — bilateral corticonuclear innervation to facial nucleus upper division

Clinical testing — ask patient to close eyes tightly; weakness = inability to bury eyelashes/resist examiner opening lids

Crow’s feet — repeated contraction draws skin toward lateral canthus → radiating folds; become permanent with age

Ectropion — orbicularis oculi paralysis → lower lid droops + turns outward → exposes conjunctiva + impairs tear drainage

Relation to lacrimal apparatus: Lacrimal sac lies behind medial palpebral ligament; anteriorly related to medial palpebral ligament + orbicularis oculi; lacrimal part of orbicularis forms sheath around sac; palpebral part closely related to lacrimal gland duct openings → removal of palpebral lacrimal gland necessitates removal of orbital part too

Orbicularis oculi is a flat, elliptical sphincter muscle of facial expression that surrounds the orbital opening and lies within the eyelids. It is supplied by the facial nerve (the nerve of the 2nd pharyngeal arch) and consists of three parts: orbital, palpebral, and lacrimal.

Orbital Part

Origin: Medial palpebral ligament, frontal process of maxilla, and nasal part of frontal bone.

Course and Insertion: The fibres form complete elliptical loops on and around the orbital margin, without interruption, returning to their point of origin (concentric rings around the orbit).

Action: Closes the eyelids tightly and forcefully. Protects the eye from intense light, wind, dust, and rain. Used in voluntary tight closure of the eye (e.g., winking, screwing up the eyes).

Palpebral Part

Origin: Medial palpebral ligament.

Course and Insertion: Sweeps laterally over the upper and lower eyelids to insert into the lateral palpebral ligament (lateral palpebral raphe). A small group of fibres along the lid margins forms the ciliary bundle (pars ciliaris/muscle of Riolan).

Action: Closes the eyelids gently, as in blinking and sleep.

Lacrimal Part

Origin: Posterior lacrimal crest and lacrimal fascia, lying behind the lacrimal sac, forming a sheath for the sac.

Course and Insertion: Passes laterally in front of the tarsal plates of both eyelids to the lateral palpebral raphe.

Action: Dilates the lacrimal sac by exerting traction on the lacrimal fascia, helping draw lacrimal fluid (tears) from the lacus lacrimalis into the sac via the lacrimal puncta and canaliculi — the “lacrimal pump” mechanism. Also supports the lower eyelid.

Nerve Supply

Motor supply is from the facial nerve (CN VII):

• The temporal branch supplies the frontalis, auricular muscles, and orbicularis oculi.
• The zygomatic branch also supplies orbicularis oculi.

Clinical Correlation

Bell’s Palsy: Lower motor neuron lesion of the facial nerve at or near the stylomastoid foramen. Paralysis of orbicularis oculi results in:

• Widening of the palpebral fissure and inability to close the eye (lagophthalmos).
• Tears flowing down the face (epiphora), due to paralysis of the lacrimal part and failure of the lacrimal pump.
• Loss of horizontal forehead wrinkles (due to associated occipitofrontalis paralysis).

In upper motor neuron (supranuclear) lesions, the upper part of the face — including frontalis and orbicularis oculi — escapes paralysis because these muscles receive bilateral corticonuclear (corticobulbar) innervation from the cerebral cortex.

Clinical Testing: Orbicularis oculi is tested by asking the patient to close the eyes tightly; weakness manifests as inability to bury the eyelashes or resist the examiner gently opening the lids.

Crow’s Feet: Repeated contraction of the entire orbicularis oculi draws the skin of the forehead, temple, and cheek toward the lateral angle of the eye, producing radiating skin folds from the lateral canthus. With age, these can become permanent (“crow’s feet”).

Ectropion: Paralysis of orbicularis oculi causes the lower eyelid to droop and turn outward (ectropion), exposing the conjunctiva and impairing the tear drainage mechanism.

Relation to Lacrimal Apparatus

The lacrimal sac lies in the lacrimal groove behind the medial palpebral ligament. Anteriorly, it is related to the medial palpebral ligament and the orbicularis oculi; laterally, it is related to the lacrimal fascia and the lacrimal part of orbicularis oculi, which forms a sheath around the sac. Because the palpebral part of orbicularis oculi is closely related to the ducts of the lacrimal gland opening into the conjunctival sac, removal of the palpebral part of the lacrimal gland necessitates removal of the orbital part as well.

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