Head and Neck Muscles--- Functions

splenius capitis

acting unilaterally, produce ipsilateral flexion and slight rotation of head; extend head when acting bilaterally

orbicularis oculi

closes eye in blinking, squinting, and sleep; aids in flow of tears across eye

orbicularis oris

closes lips, protrudes lips as in kissing; uniquely developed in humans for speech

buccinator

compresses cheek against teeth and gums; directs food between molars; retracts cheek from teeth when mouth is closing to prevent biting cheek; expels air and liquid

hyoglossus

depresses tongue

depressor anguli oris

draws angle of mouth laterally and downward in opening mouth or sad expressions

risorius

draws angle of mouth laterally in expressions of laughing, horror, or disdain

zygomaticus major

draws angle of mouth upward and laterally in laughing

platysma

draws lower lip and angle of mouth downward in expressions of horror or surprise; may aid in opening mouth widely

depressor labii inferioris

draws lower lip downward and laterally in chewing and expressions of melancholy or doubt

styloglossus

draws tongue upward and posteriorly

levator labii superioris

elevates and everts upper lip in sad, sneering, or serious expressions

mentalis

elevates and protrudes lower lip in drinking, pouting, and expressions of doubt or disdain; elevates and wrinkles skin of chin

levator anguli oris

elevates angle of mouth as in smiling

frontalis

elevates eyebrows in glancing upward and expressions of surprise or fright; draws scalp forward and wrinkles skin of forehead

palatoglossus

elevates root of tongue and closes oral cavity off from pharynx

levator scapulae

elevates scapula if cervical vertebrae are fixed; flexes neck laterally if scapula is fixed, retracts scapula and braces shoulder; rotates scapula and depresses apex of shoulder

zygomaticus minor

elevates upper lip, exposes upper teeth in smiling or sneering

masseter

elevation of the mandible, with smaller roles in protraction, retraction, and lateral and medial excursion

temporalis

elevation, retraction, and lateral and medial excursion of the mandible

semispinalis capitis

extend and contralaterally rotate head

trapezius

extends and laterally flexes neck

temporal, zygomatic, buccal, mandibular, cervical

five branches of facial nerve

galea aponeurotica

flat tendinous sheath under the scalp, not a muscle; connects frontalis and occipitalis

trigeminal nerve

largest of the cranial nerves, most important sensory nerve of face; chewing, touch, temperature, pain sensations from upper face (V)

facial nerve

major motor nerve of the facial muscles (VII)

glossopharyngeal nerve

mixed nerve with numerous sensory and motor functions in the head, neck, and thoracic regions (IX)

vagus nerve

most extensive distribution of any cranial nerve; plays major roles in the control of cardiac, pulmonary, digestive, and urinary functions (X)

accessory nerve

nerve that controls mainly swallowing and neck and shoulder muscles; does not arise from brain -> arises from upper spinal cord (XI)

occipitalis

retracts scalp; fixes galea aponeurotica so frontalis can act on eyebrows

genioglossus

unilateral action draws tongue to one side; bilateral action depresses midline of tongue or protrudes tongue

sternocleidomastoid

unilateral action tilts head slightly upward and toward the opposite side; most common action is probably rotating the head to the left or right

scalenes

unilateral contraction causes ipsilateral flexion or contralateral rotation; bilateral contraction flexes neck