5 muscles:
- Frontal Belly/Frontalis: draws scalp anteriorly, wrinkles skin of forehead horizontally, raises eyebrows
- Orbicularis oculi: closes eye
- Orbicularis oris: purses lips, puckers lip edges, closes and protrudes lips
- Buccinator: helps with mastication (chewing) by keeping food between the teeth (and not between teeth and cheeks) and assists in whistling, blowing, and sucking by pressing cheeks against teeth and lips. It also draws the corner of the mouth laterally.
- Platysma: depresses mandible, draws outer part of lower lip inferiorly and posteriorly as in pouting
Mechanism of Muscle Weakness: Bell’s palsy is due to a damage to or illness of the facial (VII) nerve. Possible causes include ear infections that inflame the facial nerve, ear surgery that harms the face nerve, and herpes simplex virus infection. It can also be due to damage of myelin sheath and impaired immunity from stress, sleep deprivation, physical trauma, minor illness, or autoimmune syndromes. In severe situations, the paralysis makes the entire side of the face droop. On the affected side, they are unable to furrow their brow, close their eyes, or purse their lips.
Symptoms:
- Sudden facial paralysis or weakening on one side
- A drooping brow
- Drooling from one side of the mouth
- Having trouble closing the eyes leading to eye dryness
- Pain around the jaw or around the ear
References:
National Institute of Neurological Disorders and Stroke. (n.d.). Bell’s Palsy. Retrieved September 8, 2023, from https://www.ninds.nih.gov/health-information/disorders/bells-palsy
Tortora, G. J., & Derrickson, B. (2017). Principles of Anatomy and Physiology (15th ed.) [Online]. https://handoutset.com/wp-content/uploads/2022/05/Principles-of-anatomy-and-physiology-Wiley-2017-Derrickson-Bryan-H._-Tortora-Gerard-J..pdf