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Pars orbitalis

Other Terms: Pars orbitalis (Musculus orbicularis oculi), Pars orbitalis musculus orbicularis oculi

Muscle parts

Palpebral part with a ciliary bundle and deep part; Orbital part

Latin name

Musculus orbicularis oculi

Latin muscle parts

Pars palpebralis with fasciculus ciliaris and pars profunda; Pars orbitalis

Group

Branchial arch muscle – second arch (Facial muscle)

Etymology

The English name for this muscle is the little circle muscle of the eye. The word orbicularis comes from the Latin orbis meaning “circle or disk” and ulus which is a diminutive ending meaning “little.” The word oculi is from the Latin oculus meaning “eye.”

Origin

The orbital part arises from the frontal and adjacent maxillary bones, the palpebral part arises from the medial palpebral ligament and adjacent bone, and the lacrimal part arises from the lacrimal bone

Insertion

The orbital part forms circular fibers that wrap around the eye and blend with various neighboring muscles on all sides of the orbit, the palpebral fibers cross the both eyelids to blend with each other on the lateral side of the eye, and the lacrimal part of the muscle sends fibers to the tarsi of the superior eyelid and blends with fibers on the lateral side of the eye.

Action

The complexly arranged fibers of this muscle account for a variety of muscle functions. Its palpebral fibers are involved in reflexive blinking and soft closure of the eyelids. The deeper fibers are involved with the more forceful sphincter-like closure of the eye. Contraction of the muscle also helps express tears from the lacrimal gland and distribute the tears across the surface of the eye. The medial fibers help project the puncta lacrimale into the lacus lacrimale to aid in draining the tears from the eye’s surface and moving them through the lacrimal sac and duct.

Nerve supply

Facial nerve (Cranial nerve VII)

Blood supply

Terminal portion of the facial artery; zygomatico-orbital branch of the superficial temporal artery; supraorbital and supratrochlear branches of the ophthalmic artery.

Latin

Pars orbitalis musculus orbicularis oculi

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