muscle of head and neck actions of AOI

frontal belly

raises eyebrows

occipital belly

fixes aponeurosis and pulls scalp posteriorly

orbicularis oculi

closes eyes

orbicularis oris

closes lips

zygomaticus

raises lateral corners of mouth upward

masseter

prime mover of jaw closure

temporalis

closes jaw

medial pterygoid

in conjunction with lateral pterygoid, aids in grinding movements of teeth

lateral pterygoid

aids in grinding movements of teeth

platysma

tenses skin of neck

sternocleidomastoid

flexion of neck, rotate head toward shoulder on opposite side

digastric

elevate hyoid bone, open mouth and depress mandible

stylohyoid

elevates and retracts hyoid bone

mylohyoid

elevates hyoid bone and base of tongue

sternohyoid

depresses larynx and hyoid bone

sternothyroid

depresses larynx and hyoid bone

thyrohyoid

depresses hyoid bone, elevates larynx if hyoid is fixed