There is an epicranial musculo-fibrous sheet in our scalp extending from forehead right up to the top of skull and backside of the skull. This muscle helps in raising eyebrows to show horror, surprise or doubt. Entire scalp can be moved by alternately moving frontalis and occipitalis i.e. the front and back parts of this muscle.
Australopithecus robustus, was a human ancestor living a million and half years ago. They had a cranial crest running in midline of the dome of skull. On either side of this crest were muscles which probably moved the scalp much more extensively and forcefully than we are capable of.
Around the external ear are three small muscles that allow some people to twitch their pinna a little. But they are not important in showing or changing the human facial expression. A dog or cat can prick the ears and orient them to source of sound with these ear muscles. Around our eyelid are the orbicularis oculi muscles in the form of a ring. These muscles help us in voluntary and involuntary blinking, and control tear duct.
Around the nose there are several small muscles, like procerus, nasalis, depressor septi. With the help of these muscles we can frown, flare or compress the nostrils.
The mouth is surrounded by muscles like - elevators, retractors and evertors of upper and lower lips and a circular ring of muscles orbicularis oris. Orbicularis oris causes closing of the mouth, and rounding and protrusion of the lips. The buccinators, (from buccina, a trumpet) which are at the side of face between the two jaws help in compressing the cheeks.
Some of the facial muscles are just broad thin sheets like the - Quadratus labii superioris. This muscle helps in raising the upper lip upward.
Most of the muscles of facial expression are around the eyes, nose and mouth i.e. our bodies "windows to the world". These muscles are subcutaneous that is just beneath the skin and unlike other skeletal muscles some of them are not attached to the bones.
The facial muscles can pull the corners of the mouth up or down, show grin, displeasure, puff, grimace etc. They also help in eating food and in chewing it.
If the facial muscles are healthy and well toned the face looks younger and brighter.
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