The seventh cranial nerve is the facial nerve in which they carry nerve fibers that enable movement in the face as well as produce facial expressions. Furthermore, this is also responsible for the taste of the ⅔ anterior of tongue and production of tears (as lacrimal gland).
The following muscles are involved in the movement made about by seventh cranial nerve:
Frontal (temporal), Zygomatic (eye closure), Buccal (movement of lip, nostril, spontaneous eye blinking, raising corner of mouth), marginal mandibular branch (depression of lower lip), cervical (lower chin)
When the nerve is damaged or is infected with a viral infection, this can result to injury to the nerve and may affect the following:
Frontal: Inability to move eyebrows due to paralysis of forehead (can impair vision)
Zygomatic: Movement to close the eyes is of difficulty
Buccal: difficulty in motion of mouth. May result in problems in speech because some sound needs to be articulated to produce the word. Furthermore nasal obstruction may also appear.
Marginal Mandibular: infection of this muscle may result to asymmetric smile
Cervical: paralysis of platysma muscle. May contribute to lower lip asymmetry when smiling.
Reference: What is the Facial Nerve? (2020). Otolaryngology — Head & Neck Surgery. https://med.stanford.edu/ohns/OHNS-healthcare/facialnervecenter/about-the-facial-nerve.html#:~:text=The%20facial%20nerve%20is%20the,producing%20tears%20(lacrimal%20gland).