ACTIVITY 1
1. Platysma
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Origin: Fascia over deltoid and pectoralis major muscles.
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Insertion: Mandible, blends with muscles around angle of mouth, and skin of lower face.
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Action: Draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible.
2. Mentalis
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Origin:Incisive fossa of mandible.
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Insertion: Skin of chin (Mentolabial sulcus)
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Action: Elevates and protrudes lower lip and pulls skin of chin up, as in pouting.
3. Orbicularis Oris
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Origin: Muscle fibers surrounding opening of mouth.
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Insertion: Skin at corner of mouth.
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Action: Closes and protrudes lips, as in kissing; compresses lips against teeth; and shapes lips during speech.
4.Corrugator supercilii
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Origin: Medial end of superciliary arch of frontal bone.
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Insertion: Skin of eyebrow.
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Action: Draws eyebrow inferiorly and wrinkles skin of forehead vertically as in frowning.
5. Orbicularis oculi
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Origin: Medial wall of orbit
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Insertion: Circular path around orbit.
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Actions: Closes eye.
6. Occipitofrontalis (particularly frontal belly)
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Origin: Epicranial aponeurosis.
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Insertion: Skin superior to supraorbital margin.
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Action: Draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally as in look of surprise.
References:
Tortora, G. J., & Derrickson, B. H. (2016, December). Principles of Anatomy and Physiology. (15th Ed., pp.341 - 342). John Wiley & Sons Inc.
Vaskovic. (2023, April 12). Mentalis muscle. https://www.kenhub.com/en/library/anatomy/mentalis-muscle