Physio Muscle Quiz 10.14

Front 1

pectoralis major

Back 1

prime mover of arm flexion; rotates arm medially; adducts arm against resistance; with scapula (and arm) fixed, pulls rib cage upward, thus can help in climbing throwing, pushing, and in forced inspiration

Front 2

latissimus dorsi

Back 2

prime mover of arm extension; powerful arm adductor; medially rotates arm at shoulder; depresses scapula; because of its power in these movements, it plays an important role in bringing down the arm in a power stroke, as in striking a blow, hammering, swimming, and rowing with arms fixed overhead, it pulls the rest of the body upward and forward

Front 3

deltoid

Back 3

prime mover of arm abduction when all its fibers contract simultaneously; antagonist of pectoralis major and latissimus dorsi, which adduct the arm; if only anterior fibers active can act powerfully in flexion and medial rotation of humerus, therefore synergist of pectoralis major of only posterior fibers are active, effects extension and lateral rotation of arm; active during rhythmic arm movements during walking

Front 4

subscapularis

Back 4

chief medial rotator of humerus; assisted by pectoralis major, helps to hold head of humerus in glenoid cavity, thereby stabilizing shoulder joint

Front 5

supraspinatus

Back 5

stabilizes shoulder joint; helps to prevent downward dislocation of humerus, as when carrying a heavy suitcase; assists in abduction

Front 6

infraspinatus

Back 6

helps to hold head of humerus in glenoid cavity, stabilizing the shoulder joint; rotates humerus laterally

Front 7

teres minor

Back 7

same actions as infraspinatus muscle; adducts arm

Front 8

teres major

Back 8

posteromedially extends, medially rotates and adducts humerus; synergist of latissimus dorsi

Front 9

coracobrachialis

Back 9

flexion and adduction of the humerus; synergist of pectoralis major

Front 10

triceps brachii

Back 10

powerful forearm exterior (prime mover, particularly medial head); antagonist of forearm flexors; long and lateral heads mainly active in extension against resistance; long head tendon may help stabilize shoulder joint and assist in arm adduction

Front 11

anconeus

Back 11

abducts ulna during forearm pronation; synergist of triceps brachii in elbow extension

Front 12

biceps brachii

Back 12

fixes elbow joint and supinates forearm; these actions usually occur at the same time (e.g. when you open a bottle of wine, it turns the corkscrew and pulls the cork); weak flexor of arm at shoulder

Front 13

brachialis

Back 13

a major forearm flexor (lifts ulna as biceps lift the radius)

Front 14

brachioradialis

Back 14

synergist in forearm flexion; acts to best advantage when forearm is partially flexed and semi-pronated; during rapid flexion and extension, stabilizes the elbow