8.8 Muscle Actions

Front

This muscle closes the eye.

Back

orbicularis oculi

Front

Closes and protrudes lips.

Back

orbicularis oris

Front

elevates and protracts the mandible

Back

masseter

Front

elevates and retracts the mandible

Back

temporalis

Front

laterally flexed head and neck to the same side, rotates head to the opposite side. Pulls the head forward and down; also aid in forceful inhalation by elevating sternum and first ribs.

Back

sternocleidomastoid

Front

Rotates and retracts scapula Superior portion elevates scapula Inferior portion depresses scapula

Back

trapezius

Front

Flexes arm at shoulder, adducts and medially rotates arm

Back

pectoralis major

Front

Extends arm at shoulder, adducts and medially rotates arm

Back

teres major & latissimus dorsi

Front

lateral portion abducts arm; anterior portion flexes arm at shoulder; posterior portion extends arm at shoulder

Back

deltoid

Front

Flexes forearm at elbow, supinates forearm and hand

Back

biceps brachii