We blink up to 20 times a minute and wink to convey complicity. This is thanks to the orbicularis oculi muscle, the subtle muscle keeping your eyes safe from bright lights, touch and foreign objects, even faster than you can think about it.
Orbicularis Oculi‘ fibers flow laterally, creating a thin layer where the eyelids are (palpebrae). This sphincter muscle surrounds the orbit of the eyeball but also covers the temples and a bit of the cheek. It’s usually divided into three sections: orbital, palpebral and lacrimal.
The orbital section appears to be thicker, with fibers taking the shape of an continuous ellipse at the lateral palpebral commissure. At the top, these fibers blend into the corrugator muscle and the frontalis muscle (frontal belly of the occipitofrontalis). It is presumed that this portion of orbicularis oculi is responsible for strong closing of the eyelids.
The palpebral section of the muscle has a thin and pale appearance, forming concentric circles that originate from the medial palpebral ligament and then inserts into the lateral palpebral raphe. It’s presumed that this portion of the orbicularis oculi muscle is responsible for spontaneous blinking.
The lacrimal part is much smaller and thinner than it’s other two counterparts. It sits behind the lacrimal sac and the medial palpebral ligament. This part of orbicularis oculi allows for easier pumping of tears into the lacrimal sac. It’s composed from the posterior crest and part of the lacrimal bone, then divides into upper and lower and is inserted into the punta lacrimalia, sometimes both parts are indistinguishable.
What does the Orbicularis oculi Muscle do?
Orbicularis oculi’s function is to blink and wink. You use it to close and keep your eyes closed. Also, involuntary blinking keeps the tear film spread over the eye, keep it lubricated. But also, when we hear a sudden loud noise, something gets too close to your eyes too quickly, something touches the conjuntiva, cornea or cilia would trigger the eyelids to close. It makes you wonder why evolution came up with these mechanism to protect the eye, what chain of events led to these actions to be integrated into us?
This protective reflex is called blepharospasm (blepharos means eyelid), and blinking of the eyes is an example of an unconditioned reflex. It could be that someone blows a little bit of air and it will probably not hurt your eyes but still trigger the blinking reflex.
When the orbital part of the muscle contracts, it makes the eyes be closed tightly. Blinks and winks involve the contraction of the palpebral part of the Orbicularis oculi.
A lot of people get surgeries to lift they eyelids and stretch the skin and inject Botox to hide away their ageing faces. All this would suggest that the orbicularis oculis probably gets more lax with age right? Well, think again, it was demonstrated in this study that this particular muscle shows no sign of aging. Isn’t it wonderful that we blink all of our lives and this muscle just keeps on giving?
Facial nerve (VII)
- Ophtalmic Artery
- Zygomatico-orbital artery
- Angular artery
Orbicularis Oculi origin
- Frontal bone
- Medial palpebral ligament
- Lacrimal bone
Orbicularis Oculi Insertion
Lateral palpebral raphe
Standring, Susan. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. , 2016. Print.