1.) Muscles affected and its actions
A.
Muscle: Orbicularis oris
Action: Closes and protrudes lips, as in kissing; compresses lips against teeth; and shapes lips during speech
B.
Muscle: Orbicularis oculi
Action: Closes eye
C.
Muscle: Buccinator
Action: Presses cheeks against teeth and lips, as in whistling, blowing, and sucking; draws corner of mouth laterally; and assists in mastication (chewing) by keeping food between the teeth (and not between teeth and cheeks).
D.
Muscle: Platysma
Action: Draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible
E.
Muscle: Occipitofrontalis
Action: Draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally as in look of surprise.
2.) Mechanism of muscle weakness
The Facial (VII) nerve which control facial muscles travels via a narrow corridor of bone on its way to the face. The nerve becomes inflamed and swollen in Bell's palsy (Bell’s Palsy - Symptoms and Causes - Mayo Clinic, 2022). Hence, the weakness of the aforementioned muscles.
3.) Symptoms
- Paralysis or sudden weakness on one side of patient's face
- Dropping eyebrow
- Drooling from one side of patient's mouth
- Difficulty closing an eyelid, which results to eye dryness
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 - 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.