ACTIVITY 1
1. Platysma
- Origin: Facia over deltoid and pectoralis 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
2. Mentalis
- Origin: Mandible
- Insertion: Skin of chin
- Action: Elevates and protrudes lower lip and pulls skin of chin up, as in pouting
3. 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
4. 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
5. Orbicularis oculi
- Origin: Medial wall of orbit
- Insertion: Circular path around orbit
- Action: Closes eye
6. 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
Reference:
Tortora, G. J., & Derrickson, B. (2017). Principles of anatomy and physiology (15th ed., pp. 341–342). Wiley.