Muscles to Know - Anatomy

frontalis

location: forehead (frontal bone)

function: lifts eyebrows/pulls scalp up

temporalis

location: sits on temporal bone, attaches to mandible

function: assists the act of chewing

masseter

location: side of mandible

function: powerful chewing muscle, closes jaw

orbicularis oculi

location: around the eyes

function: closing the eyes (voluntary winking)

orbicularis oris

location: around the mouth

function: puckering the lips

zygomaticus

location: on the zygomatic bone, attached to the corners of the mouth

function: smiling

platysma

location: front of neck

function: pulls the jaw down

sternocleidomastoid

location: sides of the neck, base of skull to sternum

function: lateral rotation of the head

triceps brachii

location: posterior side of humerus

function: extension of the lower arm at the elbow

biceps brachii

location: anterior side of the humerus

function: flexion of the lower arm (elbow flexion)

trapezius

location: upper back, back of neck

function: stabilizes the scapula, head, and neck; shrugs shoulders

deltoid

location: top of the shoulders

function: arm abduction

pectoralis major

location: anterior of chest across the ribcage

function: arm flexion at the shoulder joint

external oblique

location: anterior of abdomen, most superficial of the ab muscles

function: helps rotational movement

transverse abdominis

location: under obliques, deepest ab muscle, wraps around trunk front to back

function: provides intraabdominal pressure for things like blowing out candles

rectus abdominis

location: front of the abdomen, “six pack”

function: protects organs, transfer of power between upper and lower body

internal oblique

location: under external obliques, beside rectus abdominis

function: abdominal movement, especially bending

diaphragm

location: in the ribcage, under the lungs

function: primary muscle for breathing, pulls lungs down as it contracts

latissimus dorsi

location: on the back

function: all pulling and rowing motions (arm/shoulder adduction)

rectus femoris

location: quad, attached at hip and patella, crosses hip joint, covers vastus intermedius

function: knee extension

vastus lateralis

location: quad, lateral most of the three

function: knee extension

vastus intermedius

location: quad, middle of the three, hidden by rectus femoris

function: knee extension

vastus medialis

location: quad most medial of the three

function: knee extension

biceps femoris

location: hamstring, inserts on fibula, crosses over from ischium

function: knee flexion

semitendinosus

location: hamstring, inserts on tibia, more lateral

function: knee flexion

semimembranosus

location: hamstring, inserts on tibia, more medial

function: knee flexion

gluteus maximus

location: buttocks

function: hip extension (pulling leg back), one of strongest muscles

sartorius

location: thigh, crosses over quad muscles

function: hip flexion but mainly external rotation of the hip

adductor magnus

location: inside of thigh

function: adduction of hip

gracilis

location: groin

function: adduction of the leg

iliopsoas (psoas major+iliacus)

location: hip near iliac crest

function: powerful hip flexor

piriformis

location: inside hip

function: depends on position of leg - external rotation when extending, abduction of leg when flexing

iliotibial tract and TFL

location: lateral side of thigh

function: stabilizes hip and knee during activity

gastrocnemius

location: calf, further from tibia, crosses ankle and knee joints

function: plantar flexion, power for jumping and sprinting

soleus

location: covered by gastrocnemius, in calf

function: aids plantar flexion, used to stabilize ankle when standing for long periods

tibialis anterior

location: shin (anterior of tibia)

function: dorsiflexion (pulling foot up)

agonist

lead muscle in creating a force

antagonist

the opposing muscle to the prime mover

synergist

helps the prime mover with extra force and control of movement

fixators

muscles that immobilize a bone

movement, support, protection, heat generation

major functions of muscles

origin

the tendon attachment at the less moveable part

insertion

the tendon attachment at the more moveable part

excitability

the ability to be stimulated and show a response

contractivity

the ability to shorten upon stimulation

extensibility

the ability to lengthen beyond resting value

elasticity

ability to return to original position

skeletal

type of muscle that allows movement

cardiac

muscles around the heart

smooth

muscles around intestines, blood vessels, uterus, and hollow organs

abduction

move away from the body

adduction

move toward the body

extension

joint angle increases

flexion

joint angle decreases

dorsiflexion

pulling foot up toward tibia

plantar flexion

moving ankle down away from tibia

vertical

direction of fibers in rectus abdominus

horizontal

direction of fibers in transverse abdominis

down and in

direction of fibers in external oblique

up and into rib cage

direction of fibers in internal oblique