ACTIVITY 1
Name a muscle that may cause the following facial expression and write down its origin, insertion, and action.
1. PLATYSMA
- a. Origin: Fascia over deltoid and pectoralis major muscles.
- b. Insertion: Mandible, blends with muscles around angle of mouth, and skin of lower face
- c. Action: Draws outer part of lower lip inferiorly; depresses mandible.
2. MENTALIS
a. Origin: Mandible
b. Insertion: Skin of chin
c. Action: Elevates and protrudes lower lip and pulls skin of chin up, as in pouting
3. ORBICULAR ORIS
a. Origin: Muscle fibers surrounding opening of mouth
b. Insertion: Skin at corner of mouth
c. Action: Closes and protrudes lips, as in kissing; compresses lips against teeth
4. CORRUGATOR SUPERCILII
a. Origin: Medial end of superciliary arch of frontal bone.
b. Insertion: Skin of eyebrow
c. Action: Draws eyebrow inferiorly and wrinkles skin of forehead vertically as in frowning.
5. ORBICULARIS OCULI
a. Origin: Medial wall of orbit
b. Insertion: Circular path around orbit
c. Action: Closes eye
6. OCCIPITOFRONTALIS (FRONTAL BELLY)
a. Origin: Epicranial aponeurosis
b. Insertion: Skin superior to supraorbital margin.
c. Action: Draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally (surprised look).