They generally originate from the surface of the skull bone (rarely the fascia), and insert on the skin of the face.

In humans, they typically begin forming around the eighth week of embryonic development.

[1] An inability to form facial expressions on one side of the face may be the first sign of damage to the nerve of these muscles.

Paralysis is the loss of voluntary muscle action; the facial nerve has become damaged permanently or temporarily.

These situations of paralysis not only inhibit facial expression but also seriously impair the patient’s ability to speak, either permanently or temporarily.