ACTIVITY 1
I. Platysma
- Origin: Fascia over deltoid and pectoralis major muscles.
- Insertion: Mandible, blends with muscles around angle of mouth, and skin of lower face.
- Action: Draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible.
II. Mentalis
- Origin: Mandible.
- Insertion: Skin of chin.
- Action: Elevates and protrudes lower lip and pulls skin of chin up, as in pouting.
III. Orbicularis oris
- origin: Muscle fibers surrounding opening of mouth.
- insertion: Skin at corner of mouth.
- action: Closes and protrudes lips, as in kissing; compresses lips against teeth; and shapes lips during speech.
IV. corrugator supercilii
- origin: Medial end of superciliary arch of frontal bone.
- insertion: Skin of eyebrow.
- action: Draws eyebrow inferiorly and wrinkles skin of forehead vertically as in frowning.
V. orbicularis oculii
- origin: Medial wall of orbit.
- insertion: Circular path around orbit.
- action: Closes eye.
VI. Occipitofrontalis (frontal belly)
- Origin: Epicranial aponeurosis
- Insertion: Skin superior to supraorbital margin.
- Action: Draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally as in look of surprise.