ACTIVITY 1
Name the muscle that may cause the following facial expression and write down its origin, insertion and action.
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PLATYSMA
Origin: Fascia over deltoid and pectoralis major
Insertion: Mandible blends with muscles around the mouth and skin of the lower face
Action: Draws the outer part of the lower lip inferiorly, depresses the mandible
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MENTALIS
Origin: Mandible
Insertion: Skin of the chin
Action: Elevates and protrudes lower lip and pulls skin of the chin up
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ORBICULARIS ORIS
Origin: Muscle fibers surrounding the opening of the mouth
Insertion: Skin at the corner of the mouth
Action: Closes and protrudes lips, compresses lips against teeth, shapes lips during speech
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CORRUGATOR SUPERCILII
Origin: Medial end of superciliary arch of frontal bone
Insertion: Skin of eyebrow
Action: Draws eye inferiorly, wrinkles skin of forehead vertically (frowning)
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ORBICULARIS OCULI
Origin: Medial wall of orbit
Insertion: Circular path around orbit
Action: Closes eyes
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OCCIPITOFRONTALIS
Frontal Belly Origin: Epicranial aponeurosis
Occipital Belly Origin: Occipital bone and mastoid process of temporal bone
Frontal Belly Insertion: Skin superior to supraorbital margin
Occipital Belly Insertion: Epicranial aponeurosis
Action: Draws scalp anteriorly/posteriorly, raises eyebrows, and wrinkles skin of forehead horizontally