Muscles
1. Frontalis - elevates the eyebrows and wrinkles the forehead
2. Orbicularis oculi - closes the eye
3. Zygomaticus major - elevates the corner of mouth as in smiling
4. Buccinator - presses cheeks against teeth and lips
5. Orbicularis Oris: closes and protrudes the lips
Mechanism: It is caused by damage of the facial nerve which is responsible in transmitting signals to the facial muscles. It can also be cause by inflammation or compression of facial nerve due to an ear infection, or herpes simplex virus. The disorder causes paralysis or weakness of facial muscles in one side.
Symptoms: difficulty closing the eye, drooling, weakness in chewing