Anatomy Muscles Actions

Action of Occipitofrontalis

• raises eyebrow and pulls scalp posterior

• closes lips

• raises eyebrow and pulls scalp anterior

• allows squinting

action of Orbicularis Occuli

• Moves the eyebrows

• Closes the eyelids squint, and blink

• Widen the eyes
• Open the eyelids

action of Orbicularis oris

• Control jaw movement
• Raise the upper lip
• Close and protrude the lips, shape the lips during speech and facial expressions
• Widen the mouth

actions of the buccinator

• Raises the eyebrows
• Contracts the lips
• Compresses the cheeks against the teeth and gums
• Expands the cheeks against the teeth and gums

Actions of masseter

• Assists in closing the mouth
• Elevates the mandible during chewing
• Moves the mandible from side to side
• Depresses the mandible during chewing

action of Temporalis

• Depresses the mandible during chewing
• Protracts the mandible during chewing
• Assists in lateral movement of the mandible during chewing
• Elevates and retracts the mandible during chewing

action of Sternocleidomastoid

• Extend the neck
• Flex the head to the same side
• Rotate the head to the opposite side and flex the neck
• Rotate the neck to the same side

Actions of Erector Spinae: IIiocostalis, Longissimus, and Spinalis

• Flexion, abduction, and adduction of the vertebral column
• Extension, lateral flexion, and rotation of the vertebral column
• Dorsiflexion, plantar flexion, and pronation of the vertebral column
• Circumduction, inversion, and eversion of the vertebral column

Actions of External Intercostals

• Elevate the ribs during inhalation
• Assist in bending the trunk laterally
• Contract the diaphragm during exhalation
• Lower the ribs during inhalation

Actions of Internal Intercostals

• Contract during inhalation
• Assist in forced expiration
• Elevate the ribs and increase thoracic cavity volume
• Depress the ribs and decrease thoracic cavity volume