Muscles (Innervation and Action)

Question 1

What are the extrinsic shoulder muscles

Answer 1

Superficial posterior axioperpendicular muscles:
Trapezius
Latissimus Dorsi

Deep posterior axioperpendicular muscles:
Levator scapulae
Rhomboid minor and major

Question 2

What are the intrinsic shoulders muscles

Answer 2

Deltoid
Teres major
Supraspinatus
Infraspinatus
Teres minor
Subscapularis

Question 3

Nerves innervating Trapezius

Answer 3

Accessory nerve (CN XI/11) - motor fibers
Spinal Nerves (C3, C4) - pain and proprioceptive fibers

Question 4

Action of trapezius

Answer 4

Descending part elevates
Ascending part depresses
Middle part or all parts retracts scapula
Ascending and Descending part act together to rotate glenoid cavity superiorly

Question 5

Nerves innervating Latissimus dorsi

Answer 5

Thoracodorsal nerve (C6, C7, C8)

Question 6

Action of Lats

Answer 6

Extends, adducts, medially rotates the humerus

Raises body towards arms when climbing or pull ups

Question 7

nerves innervating levator scapulae

Answer 7

Dorsal scapular nerve (C5)
Cervical nerves (C3,C4)

Question 8

nerve innervating rhomboid minor and major

Answer 8

Dorsal scapular nerve (C4, C5)

Question 9

action of levator scapulae

Answer 9

elevate scapula, tilts glenoid cavity of scapula inferiorly

Question 10

rhomboid minor and major action

Answer 10

retract and rotate scapula

fix scapula to thoracic wall

Question 11

nerve innervating deltoid

Answer 11

axillary nerve (C5,C6)

Question 12

deltoid action

Answer 12

anterior part: flexes and medial rotation
middle part: abducts arm
posterior part: extends and lateral rotation

Question 13

nerves innervating teres major

Answer 13

lower subscapular nerve (C5, C6)

Question 14

action of teres major

Answer 14

adducts and medially rotates arm

Question 15

what are the rotator cuff muscles

Answer 15

Subscapularis
Infraspinatus
Teres minor
Supraspinatus

Question 16

nerves innervating supraspinatus

Answer 16

suprascapular nerve (C4,C5,C6)

Question 17

supraspinatus action

Answer 17

initiates and assists deltoid in abduction

acts with other rotator cuff muscles

Question 18

nerves innervating infraspinatus

Answer 18

suprascapular nerve (C5, C6)

Question 19

infraspinatus action

Answer 19

Laterally rotates arm

help hold humeral head in glenoid cavity of scapula

Question 20

nerve innervating teres minor

Answer 20

Axillary nerve (C5, C6)

Question 21

teres minor action

Answer 21

laterally rotates arm

helps hold humeral head in glenoid cavity of scapula

Question 22

nerves innervating subscapularis

Answer 22

upper and lower subscapular nerves (C5, C6, C7)

Question 23

subscapularis action

Answer 23

adducts and medially rotates arm

helps hold humeral head in gelnoid cavity of scapula

Question 24

what are the upper arm (humeral) muscles

Answer 24

biceps brachii
brachialis
coracobrachialis
triceps brachii
anconeus

Question 25

nerves innervating biceps brachii

Answer 25

Musculocutaneous nerve (C5, C6)

Question 26

biceps brachii action

Answer 26

supinates forearm
flexes forearm when supinated
short head resists dislocation of shoulder

Question 27

nerves innervating brachialis

Answer 27

musculocutaneous nerve (C5, C6)

Question 28

brachialis action

Answer 28

flexes forearm in all positions

Question 29

nerves innervating coracobrachialis

Answer 29

musculocutaneous nerve (C5,C6,C7)

Question 30

coracobrachialis actions

Answer 30

helps flex and adduct arm

resists dislocation of shoulder

Question 31

nerves innervating triceps brachii

Answer 31

radial nerve (C6, C7, C8)

Question 32

action of triceps brachii

Answer 32

chief extensor of forearm
long head resists dislocation of humerus
helps in abduction of arm

Question 33

nerves innervating anconeus

Answer 33

radial nerve (C7, C8 , T1)

Question 34

anconeus action

Answer 34

assists triceps in extending forearm
stabilizes elbow joint
abduct ulna during pronation