Muscle Actions

Epicranius (occipitofrontalis)

raises eyebrows; fixes aponeurosis and pulls scalp posteriorly

Orbicularis Oculi

closes eye

Zygomaticus

raises lateral corners of the mouth upward

Orbicularis Oris

closes lips; purses & protrudes lips

Mentalis

protrudes lower lip; wrinkles chin

Platysma

tenses skin of the neck

Masseter

prime mover of jaw closure

Temporalis

closes jaw; elevates and retracts the mandible

Buccinator

compresses cheek; holds food between teeth during chewing

Sternocleidomastoid

tenses neck; laterally rotates head

Scalenes

elevate ribs 1-2

External intercostals

pulls ribs toward one another to elevate rib cage

Internal intercostals

draws ribs together to decompress rib cage

Diaphragm

prime mover of inspiration; flattens on contraction

External oblique

flexes vertebral column; compresses abdominal wall; trunk rotation and lateral flexion

Internal oblique

flexes vertebral column; compresses abdominal wall; trunk rotation and lateral flexion

Transverse abdominis

compresses abdominal contents

Rectus abdominus

flexes the vertebral column

Pectoralis minor

draws scapula forward and inferiorly

Serratus anterior

prime mover to protect and hold scapula against chest wall; rotates scapula

Trapezius

raises, rotates, and retracts (adducts) scapula and stabilizes it

Levator scapulae

elevates and adducts scapula

Rhomboids

stabilize scapulae

Pectoralis major

prime mover of arm flexion; adducts, medially rotates arm

Deltoid

prime mover of arm abduction

Latissimus dorsi

prime mover of arm extension; adducts and medially rotates arm

Teres major

extends, medially rotates, and adducts arm

Subscapularis

medially rotates arm

Supraspinatus

initiates abductions of the arm

Infraspinatus

lateral rotation of the arm

Teres minor

lateral rotation of the arm

Triceps brachii

powerful forearm extensor

Biceps brachii

flexes and supinates forearm

Flexors of the forearm/wrist

flexes forearm

Extensors of the forearm/wrist

extends forearm

Iliopsoas (iliacus & psoas major)

flex trunk and hip joint, flex thigh; lateral flexion of vertebral column

Tensor fasciae latae

steadies trunk

Sartorius

flexes, abducts, and laterally rotates thigh; flexes leg

Quadriceps femoris (recuts femoris, vastus lateralis, medialis, and intermedius)

extends leg; rectus femoris flexes thigh*

Gracilis

adducts thigh; flexes and medially rotates leg

Adductors of the thigh

adduct and medially rotate and flex thigh

Gluteus maximus

powerful thigh extensor

Gluteus medius

abducts and medially rotates thigh

Gluteus minimus

abducts and medially rotates thigh

Hamstrings (biceps femoris, semitendinosus, semimembranosus)

extends thigh; flexes leg

Tibialis anterior

prime mover of dorsiflexion

Gastrocnemius

plantar flexes the foot

Soleus

plantar flexion