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 muscles.
Insertion: Mandible, blends with muscles around the angle of mouth, and skin of the lower face.
Action: Draws the outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible.
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Mentalis
Origin: Mandible
Insertion: Skin of the chin
Action: Elevates and protrudes the lower lip and pulls the skin chin up, pouting.
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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 the lips, acting to kiss, compresses the lips against the teeth, and shapes the lips during speech.
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Corrugator supercilii
Origin: Medial end of superciliary arch of frontal bone.
Insertion: Skin of the eyebrow.
Action: Draws eyebrow inferiorly and 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
Insertion: Skin superior to supraorbital margin
Action: Draws the scalp anteriorly, raises eyebrows, and wrinkles the skin of the forehead horizontally as if looking surprised.
[SOURCE: Tortora (13th Edition) Principles of Anatomy and Physiology]