Orbicularis Oculi Muscles
Orbicularis Oculi Muscles: Overview
Anatomy
Orbicularis Oculi Muscles are paired facial muscle that encircles the orbit and the immediate perimeter of the eye. It is composed of three parts:
- Orbital part: Thick and essential for forceful closure of the eyelids; involved in expressions such as squinting.
- Palpebral part: Thinner and responsible for gentle, involuntary blinking and eyelid closure during sleep or reflex actions.
- Lacrimal (or lacrimal) part: Small and situated near the lacrimal sac, aiding in tear drainage by compressing the lacrimal sac during eye closure.
This muscle originates from the medial orbital rim, the lacrimal bone, and the surrounding fascia, and inserts into the skin around the eyelids and the lateral palpebral ligament. It is innervated by the facial nerve (cranial nerve VII) and supplied by arteries such as the ophthalmic, facial, and superficial temporal arteries.
Function
The orbicularis oculi is primarily responsible for closing the eyelids, a vital function for ocular protection, tear distribution, and non-verbal communication. Its actions include:
- Closing the eyelids tightly (orbital part): Used during forceful blinking, squinting, or protective eyelid closure.
- Gently closing the eyelids (palpebral part): Responsible for spontaneous blinking, which spreads tears and maintains eye hydration.
- Assisting in tear drainage: The lacrimal component compresses the lacrimal sac to facilitate tear flow into the nasolacrimal duct, helping keep the eye moist and free of debris.
Clinical Relevance
- Dysfunction of the orbicularis oculi, such as from facial nerve paralysis, results in inability to close the eye, leading to dry eyes, irritation, or ulceration.
- Overactivity or hypertonicity can cause involuntary eyelid squeezing, while hollowness or weakening can lead to poor eyelid closure and sagging.
This muscle plays a crucial role in protecting the eye and supporting facial expression, making it a key focus in aesthetic and reconstructive procedures.
Summary
The orbicularis oculi is a sphincter muscle surrounding the eye, enabling eyelid closure and tear drainage, integral to eye protection and facial expression.
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References:
Bolduc A, Goudreau E, Charlebois J, Lacoste L. Anatomy and Function of the Orbicularis Oculi Muscle: Implications in Facial Expression and Ocular Protection. Clin Anat. 2024 May;37(4):545-555. doi:10.1002/ca.24290. Available at: https://onlinelibrary.wiley.com/doi/10.1002/ca.24290
