Muscles - Head and Trunk

Question 0

epicranius - occipital belly

Answer 0

bipartite muscle consisting of frontal and occipital parts, covers dome of skull

origin - occipital and temporal lobes

insertion - epicranial aponeurosis

with aponeurosis fixed, fixes aponeurosis and pulls scalp posteriorly

Question 1

Epicranius - frontal belly

Answer 1

bipartite muscle consisting of frontal and occipital parts, which covers dome of skull.

origin - epicanial aponeurosis

insertion - skin of eyebrows and root of nose

action - with aponeurosis fixed, frontal belly raises eybrows

Question 2

orbicularis oculi

Answer 2

tripartite sphincter muscle of eyelids

origin - frontal and maxillary bones and ligaments around orbit

insertion - encircles orbit and inserts in tissue of eyelid

action - various parts can be activated individually: closes eyes, produces blinking, squinting, draws eyebrows inferiorly

Question 3

corrugator supercilii

Answer 3

small muscle; activity associated with that of orbicularis oculi

origin - arch of frontal bone above nasal bone

insertion - skin of eyebrow

action - draws eyebrows inferiorly and medially, wrinkles forehead vertically

Question 4

levator labii superioris

Answer 4

thin muscle between orbicularis oris and inferior eye mrgin

origin - zygomatic bone and infraorbital margin of maxilla

insertion - skin and muscle of upper lip and border of nostil

action - opens lips, raises and furrows upper lip

Question 5

zygomaticus major and minor **

Answer 5

extends diagonally from corner of mouth to cheekbone

origin - zygomatic bone

insertion - skin and muscle at corner of mouth

action - raises lateral corners of mouh upward (smiling muscle)

Question 6

risorius

Answer 6

slender muscle, runs inferior and lateral to zygomaticus

origin - fascia of masseter muscle

insertion - skin at angle of mouth

action - draws corner of lip laterally (tenses lip, zygomaticus synergist)

Question 7

depressor labii inferioris

Answer 7

small muscle from lower lip to mandible

origin - body of mandible lateral to its midline

insertion - skin and muscle of lower lip

action - draws lower lip inferiorly

Question 8

depressor anguli oris

Answer 8

small muscle lateral to depressor labii inferioris

origin - body of mandible below incisors

insertion - skin and muscle at angle of mouth below insertion of zygomaticus

action - draws corners of mouth downward and laterally; zygomaticus antagonist

Question 9

orbicularis oris

Answer 9

multilayered muscle of lips with fibers that run in many different directions; most run circularly

origin - arises indirectly from maxilla and mandible; fibers blended with fibers of other muscles associated with lips

insertion - encircles mouth; inserts into muscle and skin at angles of mouth.

action - closes lips, purses and protrudes lips (kissing/whistling muscle)

Question 10

mentalis

Answer 10

one of muscle pair forming v-shaped mass on chin

origin - mandible below incisors

insertion - skin of chin

action - wrinkles chin, protrudes lower lip

Question 11

buccinator

Answer 11

principle muscle of cheek; runs horizontally, deep to masseter

origin - molar region of maxilla and mandible

insertion - orbicularis oris

action - compresses cheek (whistling), draws corner of mouth laterally, holds food between teeth when chewing

Question 12

masseter

Answer 12

covers lateral aspect of mandibular rmus; can be palpated on forcible closure of jaws

origin - zygomatic arch and maxilla

insertion - angle and ramus of mandible

action - prime mover of jaw closure, elevates mandible

Question 13

temporalis **

Answer 13

fan-shaped muscle lying over parts of frontal, parietal, and temporal bones

origin - temporal fossa

insertion - coronoid process of mandible

action - closes jaw, elevates and retracts mandible

Question 14

platysma

Answer 14

unpaired muscle: thin, sheetlike superficial neck muscle, plays role in facial expression

origin - fascia of chest (over pectoral muscles) and deltoid

insertion - lower margin of mandible, skin, and muscle at corner of mouth

action - tenses skin of neck (depresses mandible, pulls lower lip back and down)

Question 15

sternocleidomastoid **

Answer 15

two-headed muscle located deep to platysma on anterolateral surface of neck; fleshy parts on either side indicate limits of anterior and posterior triangles of neck

origin - manubrium of sternum and medial portion of clavicle

insertion - mastoid process of temporal bone and superior nuchal line of occipital bone

action - simultaneous contraction of pair causes flexion of neck forward (vs resistance); independently, rotate head twd opposite shoulder

Question 16

digastric

Answer 16

consists of two bellies united by an intermediate tendon; assumes V shape under chin

origin - lower margin of mandible (anterior belly) and mastoid process (posterior belly)

insertion - by a connective tissue loop to hyoid bone

action - acting in concert, open mouth and depress manible. elevates hyoid bone

Question 17

sternohyoid

Answer 17

runs most medially along neck; straplike

origin - manubrium and medial end of clavicle

insertion - lower margin of body of hyoid bone

action - depresses larynx and hyoid bone (mandible fixed). may also flex skull

Question 18

mylohyoid **

Answer 18

just deep to digastric, forms floor of mouth

origin - medial surface of mandible

insertion - hyoid bone and median raphe

action - elevates hyoid bone and base of tongue during swallowing

Question 19

pectoralis major

Answer 19

large fan-shaped muscle covering upper portion of chest

origin - clavicle, sternum, cartilages of ribs 1-6, aponeurosis of external oblique muscle

insertion - fibers converge to insert by short tendon into intertubercular sulcus of humerus

action - prime mover of arm flexion, adducts, medially rotates arm, with arm fixed, pulls chest upward (forced inspiration)

Question 20

serratus anterior

Answer 20

fan-shaped muscle deep to scapula; beneath and inferior to pectoral muscles on lateral rib cage

origin - lateral aspect of ribs 1-8

insertion - vertebral border of anterior surface of scapula

action - prime mover to protract and hold scapula against chest wall; rotates scapula, causing inferior angle to move laterally and upward; essential to raising arm; fixes scapula for arm abduction

Question 21

deltoid **

Answer 21

fleshy triangular muscle forming shoulder muscle mass

origin - lateral 1/3 of clavicle; acromion and spine of scapula

insertion - deltoid tuberosity of humerus

action - acting as a whole, prime mover of arm abduction; specific fibers aid in flexion, extension, rotation of humerus

Question 22

pectoralis minor **

Answer 22

flat, thin muscle directly beneath and obscured by pec. major

origin - anterior surface of ribs 3-5, near costal cartilage

insertion - coracoid process of scapula

action - with ribs flexed, draws scapula forward and inferiorly; with scapula fixed, draws ribcage superiorly

Question 23

external intercostals

Answer 23

11 pairs lie between ribs; fibers run obliquely downward and forward toward sternum

origin - inferior border of rib above it

insertion - superior border of rib below it

action - pulls ribs toward another to elevate rib cage, aid in inspiration (antagonistic to internal intercostals)

Question 24

internal intercostals

Answer 24

11 pairs lie between ribs; fibers run deep and perpendicular to those of external intercostals

origin - superior border of rib below it

insertion - inferior border of rib above it

action - draws ribs together to depress rib cage; aid in forced expiration, antagonistic to external intercostals

Question 25

rectus abdominus

Answer 25

medial superficial muscle, extends from pubis to rib cage, ensheathed by aponeurosis of oblique muscles, segmented

origin - pubic crest and symphysis

insertion - xiphoid process and costal cartilages of ribs 5-7

action - flexes and rotates vertebral column; increases abdominal pressures, fixes and depresses ribs, stablizes pelvis during walking

Question 26

external oblique

Answer 26

most superficial lateral muscle; fibers run downward and medially; ensheathed by aponeurosis

origin - anterior surface of last 8 ribs

insertion - linea alba, pubic crest and tubercles, iliac crest

action - synergist rectus abdominus; compresses abdominal wall, aids in trunk rotation and lateral flexion

Question 27

linea alba

Answer 27

narrow, tendinous sheath that runs along the middle of the abdomen from sternum to pubic symphysis. formed by fusion of aponeuoses of external oblique and transversus muscles

Question 28

trapezius

Answer 28

most superficial muscle of posterior thorax; broad origin/insertion

origin - occipital bone, ligumentum nuchae, spines of c7 and all thoracic vertebrae

insertion - acromion and spinous process of scapula; lateral third of clavicle

action - raises, rotates, and retracts (adducts) scapula and stabilizes; extends head; superior fibers shrug shoulders, inferior depress them

Question 29

latissimus dorsi

Answer 29

broad flat muscle of lower back (lumbar region), extensive superficial origins

origin - indirect attachment to spinous processes of llower six thoracic vertebrae, lumbar vert, last 3-4 ribs, iliac crest

insertion - floor of intertubercular sulcus of humerus

action - prime mover of arm extension, adducts and medially rotates arm; brings arm down in power stroke