5 muscles affected:
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Orbicularis oculi
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Action: closes the eye
2. Orbicularis oris
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Action: closes and protrudes lips (kissing); compresses lips against teeth, and shapes lips during speech
3. Buccinator
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Action: it presses the cheeks against teeth and lips (as in whistling, blowing, and sucking); draws corner of mouth laterally; assists in mastication (chewing) by keeping food between the teeth
4. Occipitofrontalis
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Action: draws scalp anteriorly, raises eyebrows, wrinkles skin of forehead
5. Platysma muscle
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Action: draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible
Mechanism of the muscle weakness:
In Bell’s palsy, the nerves in the facial muscles become inflamed or injured, compressing the narrow corridor of the bone. The cause for Bell’s palsy is unknown, but it may be caused by a viral infection such as rubella, chickenpox, or cold sores. Some of these nerves stop functioning, leading to facial paralysis.
Other symptoms:
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Drooling
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Difficulty speaking, eating
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Difficulty in making facial movements
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Increased sensitivity to sound
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Loss of their sense of taste
References:
Bell’s Palsy. (n.d.). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/bells-palsy
Bell’s Palsy. (2023, March 8). Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/bells-palsy#:~:text=about%20Bell%27s%20palsy-,Bell%27s%20palsy%20is%20an%20unexplained%20episode%20of%20facial%20muscle%20weakness,other%20conditions%20such%20as%20diabetes.
Bell’s Palsy. (n.d.-b). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/bells-palsy
Bell’s palsy - Symptoms and causes - Mayo Clinic. (2022, May 4). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/bells-palsy/symptoms-causes/syc-20370028#:~:text=The%20nerve%20that%20controls%20facial,the%20middle%20of%20the%20ear.
Tortora, G. J., & Derrickson, B. (2015). Principles of Anatomy & Physiology (15th ed.) [E-book]. John Wiley & Sons, Inc.