A&P Module 3: Muscle Actions

scalenes (anterior, middle, posterior)

accessory muscles for breathing

buccinator

sucking through a straw

diaphragm

inspiration

obliques (external & internal)

twisting trunk

erector spinae (iliocostalis, longissimus, spinalis)

posture, standing upright

intercostals

stabilize chest wall

latissimus dorsi

climbing, pulling yourself up

levator scapulae

elevates scapula

masseter

mastication (chewing)

mentalis

pouting

occipitofrontalis

raising eyebrows

orbicularis oculi

squinting/blinking

orbicularis oris

kissing

pectoralis major

moving upper arm and shoulder blade

pectoralis minor

moving upper arm and shoulder blade

platysma

causes grimace lines

rectus abdominis

used during crunches

rhomboids

moves shoulder blades towards midline

serrratus anterior

pulls scapula forward

splenius capitis

looking upward

sternocleidomastoid

turning neck

sternohyoid

connects sternum and hyoid

temporalis

elevating/depressing ears

transversus abdominis

increases abdominal pressure

trapezius

stabilizes scapula, supports arm, and helps turn neck/head

zygomaticus

smiling

aconeus

supports elbow extension

biceps brachii

curls, flexes elbow/shoulder

brachialis

supports elbow flexion

brachioradialis

flexor of elbow

corachobrachialis

support shoulder flexion

deltoid

moves arm

extensor carpi ulnaris

extends wrist

extensor carpi radialis longus

extends wrist

extensor carpi radialis brevis

extends wrist

extensor digitorum

extends digits (fingers)

flexor carpi radialis

flex wrist

flexor carpi ulnaris

flex wrist

flexor digitorum profundus

flex digits only to middle phalange (fingers)

flexor digitorum superficialis

flex digits all the way to distal phalange (fingers)

infraspinatus

rotator cuff of shoulder joint

pronator teres

pronates arm

palmaris longus

weak wrist flexor

subscapularis

rotator cuff (anterior/medial rotation)

supinator

supinates arm

supraspinatus

rotator cuff (abducts)

teres major

adduction of arm

teres minor

rotator cuff

triceps brachii

extension of elbow and shoulder

adductor (longus, brevis, magnus)

moves leg to midline

hamstrings (biceps femoris, semitendinosus, semimembranosus)

knee flexion

extensor digitorum longus

extends digits (toes)

fibularis (longus and brevis)

everts ankle

flexor digitorum longus

flexes digits (toes)

gastrocnemius

plantar flexion

gluteus maximus

hip extension (putting leg backwards)

gluteus medius

abductor of leg

gluteus minimus

abductor of leg

gracilis

thigh adduction

iliacus

major hip flexor (with psoas major)

levator ani

elevates anus for defecation

pectineus

weak hip flexor in groin region

piriformis

stretching ankle over knee (“figure four stretch”)

plantaris

don’t need mechanically, mostly used for grafts

popliteus

unhinge knee

psoas major

major hip flexor (with iliacus)

quadratus femoris

“rotator” of hip

rectus femoris

supports knee extension

sartorius

sitting criss cross

soleus

plantar flexion

tensor fascia lata

provides integrity and tension to IT band

tibialis anterior

dorsiflexion, works with tibialis posterior to invert ankle

tibialis posterior

plantarflexion, works with tibialis anterior to invert ankle

vastus muscles (lateralis, medialis, intermedius)

support knee extension