Muscular System (Origins, Insertions, Actions)

biceps brachii

origin: long head - supraglenoid tubercle of the scapula

origin 2: short head - coracoid process of the scapula

insertion: fascia of radial and ulnar bones

action: flexes forearm

triceps brachii

origin: long head - tubercle of scapula

origin 2: lateral head - upper half of the humerus

origin 3: medial head - mid humerus

insertion: olecranon process

action: extends forearm

deltoid

origin: anterior head - lateral third of clavicle

origin 2: lateral head - acromion process

origin 3: posterior head - spine of scapula

insertion: middle of humerus

action: flexion, abduction, extension

sternocleidomastoid

origin: anterior and superior manubrium and superior medial third of clavicle

insertion: mastoid process

action: flexes and laterally rotates head

pectoralis major

origin: clavicular head - medial half clavicle

origin 2: sternocostal head - lateral manubrium and sternum, ribs 1-6

insertion: biceps groove of humerus

action: adducts arm, medially rotates arm, helps with flexion of arm

latissimus dorsi

origin: spinous process, T7-L5

insertion: twists and anchors on groove of humerus (upper end)

action: alarm adductor, extensor, and medially rotates shoulder

trapezius

origin: occipital bone to T12

insertion: lateral third of clavicle, acromion process and spine of scapula

action: elevates scapula and rotates upwards

rectus abdominis

origin: pubic crest and symphysis pubis

insertion: xiphoid process and costal cartilage

action: compresses abdomen and flexes body at hips

quadriceps: vastus medialis

origin: intertrochanteric line, medial lip of linea aspera (wraps around to anterior surface)

insertion: tibial tuberosity and patella

action: knee extension

quadriceps: vastus lateralis

origin: upper interochanteric line, base of greater trochanteric, lateral linea aspera, lateral supracondylar ridge and lateral intermuscular septum

insertion: lateral quadriceps tendon to patella, via ligamentum patellae into tubercle of tibia

action: extends knee

quadriceps: vastus intermedius

origin: anterior shaft of femur (under rectus femoris)

insertion: tibial tuberosity and patella

action: knee extension

quadriceps: rectus femoris

origin: anterior inferior iliac spine

insertion: tibial tuberosity and patella

action: extends knee, flexes hip (as in kicking a ball)

hamstrings: semimembranosus

origin: ischial tuberosity of coxal bone

insertion: posterior medial condyle of tibia

action: extends hip, flexes knee

hamstrings: semitendinosus

origin: ischial tuberosity

insertion: medial surface of proximal tibia (slightly anterior to the insertion of the semimembranosus)

action: hip extension, knee flexion

hamstrings: biceps femoris

origin: long head - ischial tuberosity

origin 2: short head - posterior midshaft of femur

insertion: head of fibula

action: hip extension, knee flexion, lateral rotation of femur

gastrocnemius

origin: lateral condyle and medial epicondyle of femur

insertion: calcaneus

action: knee flexion, plantar flexion at ankle (lowering foot)

soleus

origin: proximal third of tibia and fibula

insertion: calcaneus

action: plantar flexion at ankle (lowering foot)

gluteus maximus

origin: posterior ilium, sacrum, and coccyx

insertion: gluteal tuberosity of femur

action: extends hip (as in pushing down when climbing stairs) rotates leg laterally

temporalis

origin: frontal, parietal, and temporal lobes

insertion: coronoid process of mandible

action: elevates mandible

frontalis

origin: epicranial aponeurosis (tendon on top of head)

insertion: skin of eyebrows

action: raises eyebrows, wrinkles forehead

orbicularis oculi

origin: frontal bone and maxilla

insertion: eyelid

action: closes eye (squints) lowers eyebrows

orbicularis oris

origin: maxilla and mandible

insertion: skin and muscle around the lips

action: closes lips (purses and protrudes)

buccinator

origin: mandible and maxilla molar regions

insertion: orbicularis oris

action: compresses cheeks (whistling, sucking)

zygomatics

origin: zygomatic bone

insertion: skin and muscles at corner of mouth

action: draws up corners of mouth (as in smiling)

depressor anguli oris

origin: outer surface of mandible posterior to oblique line

insertion: modiolus at angle of mouth

action: depresses and draws angle of mouth laterally

masseter

origin: zygomatic arch and bone

insertion: mandible ramus and angle

action: elevates mandible