4.5 Shoulder/Arms Flashcards
What are the prime movers of the arm
pectoralis major
latissimus dorsi
deltoid
what are the rotator cuff muscles?
- act as synergists and fixators: originate on scapula and reinforce shoudler capsule (glenohumeral joint), prevent dislocatoin
Supraspinatus
infraspinatus
teres minor
subscapularits
what are the synergists of the muscles crossing the shoudler joint?
Coracobrachialis and teres major
Pectoralis major
*prime mover of arm
- covers superior portion of chest, forms anterior axillary fold
*divided into clavicular and sternal parts
O: clavicle, sternum, ribs 1-6, external oblique
I: humerus
*adducts and medially totates arm
*clavicle part assists in flextion, sternal part assists in extension
Deltoid
- forms rounded shoulder muscle
- O: clavicle, scapula
I: humerus
*prime mover of arm abduction when all fibers contract simulatanously
*if only anterior fibers active = flexing and rotating arm medially
*if only posterior fibers active = extension and lateral rotation of ar
Latissimus dorsi
latissimus - widest, dorsi = back
- covered by trapezius superiorly, contricutes to posterior wall of axilla
O: thoracic vertebrae, lumbar vertebrae, lower 3-4 ribs, iliac crest, and scapulae
I: humerus
*prme mover of arm extension - powerful arm adductor, medially rotates arm at shoulder
Subscapularis
- forms part of posterior wall of axilla,
O: scapula
I: humeus
*chief medial rotator of arm - assisted by pectoralis major
Supraspinatus
- located on posterior of scapula, deep to trapezius
*rotator cuff muscle
- O: scapula
I: humerus
*initiates abduction of arm - stbalizes shoulder joint
(helps prev downward disslocation)
Infraspinatus
- partially covered by deltoid and trapezius
O: scapula
I: humerus
*rotates arm laterally
*heps hold head of humerus in glenoid cavity - stabilizing shoudler joint
Teres minor
*teres = round
- elongates muscle lying inferir to infraspinatus, may be in seperable from it
- rotator cuff muscle
O: scapular
I: humerus
*same action as infraspinatus, rotates arm laterally
Teres major
- located inferiorly to teres minor
- helps form posterior wall of axilla
O: scapula
I: humerus
- extends, medially rotates and adducts arm (synergist of latissimus dorsi)
coracobachialis
O: scapula
I: humerus shaft
*flexes and adducts muscle (moves arm twds body)
what divides arm into compartments?
walls of fascia
- divides into anterior and posterior compartments
tricaps brachii
* posterior muscle, crosses elbow joint
- only muslce of posterior compantment of arm
- 3 headed origin: Long head = scapula, lateral = humerus, medial - humeral shaft
I: ulna
*powerful arm extensor, medial head is the prime mover
*antagonizes forearm flexors
*long and lateral heads mainly active in extending forearm against resistance
Anconeus
*ancon = elbow
- short triagular muslce, partially blended w. distal end of tricepts on post humerus
O: humerus
I: ulna
*may control ulnar abduction during forearm pronation
*synergist of tricepts brachii in elbow extension
Biceps brachii
- two headed, bellies unite as insertion point aproaches
O: sapula
I: radial tuberosity
*flexes and supinates forearm
Brachialis
- immediately deep to biceps brachii on distal humerus
OL humerus
: ulna
*major forearm flexor (works with biceps brachii)
Brachioradialis
*crosses eblow joint
- superficial muscle of lateral forearm
O humerus
I: radial stylod process
*synergist in flexing forewarm
what are the functions of the anterior and posterior muscles of the forarm
anterior: flexors, insert via flexor retinaculum
posterior: exteniors, insert via extensor retinaculum
actions: movement of writst, fingers, tumb and pronation/supination of forearm
how many posterir muscles are there?
- five superficial and five deep, two other muscles
- most arise from common flexor tendona attached to lateral epicondyle of humerus
- Most tendons of insertion held in place at wrist be extensor retinaculum
Superficial posterior muscles are
Brachiradialis
extensor carpi radialis longus
extensor carpi radialis brevis
extensor digitorum
extensor carpi ulnaris
Extensor carpi radialis longus
- parellels brachioradialis on lateral forarm
O: humerus
I: metacarpal
*extends hand in conjuctions w/ extensor carpi ulnaris
*abducts hand in conjunction with carpi radialis
Extensor carpi radialis brevis
- shorter and deep to extensor carpi radialis longus
- O: humerus
I: metacarpal
*extends and abducts hand - acts synergistically w. capi rad longus to steady wrist
Extensor digitorum
- medial to extensor capi radialis brevis
- detached portion of muscle = extensor digiti minimu
O: humerus
I: second to fifth fingers
*prime mover of finger extension (can extend hand and abduct fingers)
Extensor carpi ulnaris
- most medial and superficial
- O: humerus and ulna
I: metacarpal
*extends hand in conjunction w. carpi radialis and adducts hand w/ flexor carpi ulnaris
Supinator
*supination = turning palm anteriorly or upwards
- deep muscle at posterior aspect of elbow, largely concealsed by superficial muscels
I: humerus, ulna
I: radius
*assists biceps brachii ro forcibly superinate forwarm
Abductor pollicis longus
- lateral and parllel to extensor pollicis longus - distal to supinator
- O: radius and ulna
I: first metacarpal
*abducts and extends thumb
Extensor pollicis breis and longus
- deep muscle pair with common origin and action
- overlain by extensor carpi ulnaris
O: radius and ulna
I: thumb
*extends thumb
Extensor indicis
- tiny muslce close with wrist
- O: ulna
I: index finger
*extends index fiber, assists w/ wrist extending
