Muscular System | Muscle and Action

frontalis

raises eyebrows and wrinkles forehead

orbicularis oculi

blinks, squints, and pulls eyebrows down

zygomaticus

raises mouth corners (smiling)

orbicularis oris

closes, purses, and pouts lips (kissing, whistling)

buccinator

compresses cheeks and pulls mouth sideways (sucking, blowing)

platysma

pulls lower lip down and tenses neck skin

masseter

closes jaw (chewing)

temporalis

closes and retracts jaw

sternocleidomastoid

bends head forward and turns head side-to-side

erector spinae

straightens back and bends spine sideways

external intercostals

lifts ribs up to inhale

internal intercostals

pulls ribs together to exhale

rectus abdominus

flexes spine (crunches) and compresses abdomen

external oblique

twists trunk, bends spine sideways, and tightens abdomen

internal oblique

twists trunk, bends spine sideways, and tightens abdomen

transversus abdominus

tightens and compresses belly

trapezius

shrugs, moves, and stabilizes shoulder blades

pectoralis major

pulls arm forward and inward across chest

latissimus dorsi

pulls arm down and back (pulling, rowing, swimming)

deltoid

raises arm out to side

triceps brachii

straightens elbow

biceps brachii

bends elbow and rotates palm upward

flexors

flexes wrist inward

extensors

extends wrist backward

iliopsoas (= iliacus + psoas major)

lifts thigh and bends hip forward

sartorius

flexes, opens, and rotates hip; bends knee (crosses legs)

adductors

pulls thighs inward together

rectus femoris

straightens knee and lifts thigh

vastus lateralis

straightens knee

vastus medialis

straightens knee

vastus intermedius

straightens knee

gluteus maximus

pushes thigh backward (climbing, running)

gluteus medius

lifts thigh outward and balances hips while walking

biceps femoris

bends knee and pushes thigh backward

semitendinosus

bends knee and pushes thigh backward

semimembranosus

bends knee and pushes thigh backward

tibialis anterior

pulls foot upward toward shin

fibularis (peroneus) muscles

points foot downward and turns it outward

gastrocnemius

points toes downward and helps bend knee

soleus

points toes downward