ACTIVITY 1:
Name the muscle that may cause the following facial expression and write down its origin, insertion, and action.
1. Platysma
Origin: the skin and fascia of the infraclavicular and supraclavicular regions
Insertion: base of the mandible, skin of the cheek and lower lip, angle of the mouth as well as the orbicularis oris muscle
Action: depresses mandible and angle of mouth, tenses skin of the lower face and anterior neck
2. Depressor anguli oris
Origin: mental tubercle of the mandible
Insertion: modiolus and angle of the mouth
Action: contraction of this muscle causes depression of the angle of the mouth which contributes to frowning
3. Orbicularis Oris
Origin： medial aspect of the maxilla and mandible and the modiolus
Insertion: skin surrounding the lips
Action: puckers the lips and closes the mouth
4. Corrugator Supercilii
Origin: originates at the medial end of the supraorbital ridge
Insertion: skin of the forehead near the eyebrow acts as the insertion site for this muscle
Action: wrinkling of the forehead, drawing of eyebrows downwards and medially
5. Orbicularis Oculi
Origin: originates from the nasal portion of the frontal bone, frontal process of the maxilla, medial palpebral ligament as well as the lacrimal crest and lacrimal bone
Insertion: skin overlying the circumference of the orbit, the orbital septum, the temporal aspect of the orbit, and inferiorly towards the cheek
Action: closing of eyes and blinking
6. Occipitofrontalis
Origin: occipital belly originates from the occipital bone, as well as the mastoid process of the temporal bone while the frontal belly originates from the epicranial aponeurosis.
Insertion: inserts into the epicranial aponeurosis and the frontal belly inserts into the fascia of the facial muscles surrounding the eyes and the skin above the eyes.
Action: Contraction of this muscle raises the eyebrows and wrinkles the forehead.
References:
Drake, R. L., Wayne Vogl, A., Mitchell, A. (2009). Gray’s anatomy for students second edition. Elsevier health sciences.
Gilroy, A. M. (2017). Anatomy – an essential textbook (2nd edition). Thieme medical publishers.