activity 1: Name the muscle that may cause the following facial expression and write down its origin, insertion and action.
- Depressor Angular Oris: This muscle originates from the medial aspect of the maxilla and mandible, perioral skin and muscles, and modiolus. It inserts into the angle of the mouth. This muscle compresses and protrudes the lips and closes the mouth.
- Orbicularis Oris: This muscle originates from the medial region of the maxilla and mandible, perioral skin and muscles, and modiolus. It draws the corner of the mouth laterally. It also presses the mouth together and can make the mouth tight, thin, roll inward, or even thrust outward. And lastly, it inserts into the angles of the mouth.
- Buccinator: This muscle originates from the alveolar processes of maxilla and mandible, buccinator crest, and temporomandibular joint. It inserts into the fibers of the orbicularis oris, and its action is to compress and maintain the tightness of teeth, mainly while eating.
- Frontalis: The frontalis muscle inserts into the orbicularis oculi muscle and is responsible for elevating the eyebrows. Moreover, this muscle originates from epicranial aponeurosis.
- Depressor Supercilii: This muscle is responsible for the depression of the eyebrow, as the name implies. It originates from the medial orbital rim and fascia. It inserts on the medial side of the orbicularis oculi muscle’s orbital portion.
- Occipitofrontalis: This muscle wrinkles the forehead, retracts the scalp, and raises eyebrows on the frontal part. It originates from the frontal belly of the frontalis and inserts into the epicranial aponeurosis.