SHOULDER AND ARM MUSCLES

Question 1

list the 4 extrinsic shoulder muscles in the anterior compartment

Answer 1

1. pectoralis major
2. pectoralis minor
3. serratus anterior
4. subclavius

Question 2

origin, insertion, action and innervation of pectoralis major

Answer 2

• origin: clavicle, sternum, upper 6 costal cartilages
• insertion: lateral lip of bicipital groove of humerus
• action: flexion, adduction and medial rotation of humerus, draws scapula anteroinferiorly
• innervation: medial and lateral pectoral nerves C5-T1

Question 3

origin, insertion, action and innervation of pectoralis minor

Answer 3

• origin: anterior ends of ribs 3-5
• insertion: coracoid process of the scapula
• action: stabilises scapula
• innervation: medial and lateral pectoral nerves (C5-T1)

Question 4

origin, insertion, action and innervation of serratus anterior

Answer 4

• origin: ribs 1-8
• insertion: medial border of scapula
• action: protracts and holds scapula against the thoracic wall
• innervation: long thoracic nerve (C5-C7)

Question 5

origin, insertion, action and innervation of subclavius

Answer 5

• origin: superior surface of costal end of 1st rib and adjacent 1st rib cartilage
• insertion: inferior surface of middle 1/3 of clavicle
• action: stabilises clavicle
• innervation: nerve to subclavius muscle C5-C6

Question 6

list the 5 shoulder extrinsic muscles in the posterior compartment

Answer 6

1. latissimus dorsi
2. trapezius
3. levator scapula
4. rhomboid major
5. rhomboid minor

Question 7

origin, insertion, action and innervation of latissimus dorsi

Answer 7

• origin: spinous processes T7-T12, the iliac crest, ribs 8-12, and lumbodorsal fascia
• insertion: floor of inter-tubercular groove of humerus
• action: adducts, medially rotates and extends humerus, raises body towards arm in climbing
• innervation: thoracodorsal nerve C6-C8

Question 8

origin, insertion, action and innervation of trapezius

Answer 8

• origin: occipital bone, ligamentum nuchae, and spinous processes of thoracic vertebrae
• insertion: clavicle and scapula — acromion and scapula spine
• action: elevates, depresses and retracts the scapula, rotates glenoid cavity superiorly
• innervation: accessory nerve CNX1

Question 9

origin, insertion, and action of levator scapula

Answer 9

• origin: transverse processes of 1st 4 cervical vertebrae (C1-C4)
• superior angle of scapula, vertebral border of scapula
• action: elevates scapula, and inferiorly rotates glenoid cavity

Question 10

origin and insertion of rhomboid major

Answer 10

• origin: spinous processes of T2-T5 vertebrae

- insertion: vertebral border of scapula inferior to spine of scapula

Question 11

origin and insertion of rhomboid minor

Answer 11

• origin: spinous processes of vertebrae C7-T1, nuchal ligament
• insertion: vertebral border of scapula adjacent to spine of scapula

Question 12

what are the actions of the rhomboid major and minor

Answer 12

retract scapula and inferiorly rotates glenoid cavity, fix scapula to thoracic wall

Question 13

what is the innervation of levator scapula, rhomboid major and rhomboid minor?

Answer 13

dorsal scapular nerve (C5)

Question 14

list the 6 shoulder intrinsic muscles

Answer 14

1. deltoid
2. teres major
3. supraspinatus
4. infraspinatus
5. teres minor
6. subscapularis

Question 15

origin, insertion and action of deltoid

Answer 15

• origin: lateral 1/3 of clavicle, acromion and spine of scapula
• insertion: deltoid tuberosity of humerus
• action: flexes, medially rotates, abducts, extends and laterally rotates arm

Question 16

origin, insertion and action of teres major

Answer 16

• origin: posterior aspect of inferior angle of scapula
• insertion: medial lip of bicipital groove of humerus
• action: adducts and medially rotates arm (at glenohumeral shoulder joint)

Question 17

origin, insertion and action of teres minor

Answer 17

• origin: lateral border of scapula
• insertion: greater tubercle of humerus
• action: medial rotation at shoulder

Question 18

origin, insertion and action of supraspinatus

Answer 18

• origin: supraspinous fossa of scapula
• insertion: greater tubercle of humerus
• action: abduction at shoulder

Question 19

origin, insertion and action of infraspinatus

Answer 19

• origin: infraspinous fossa of scapula
• insertion: greater tubercle of humerus
• action: abduction at shoulder

Question 20

origin, insertion and action of subscapularis

Answer 20

• origin: subscapular fossa of scapula
• insertion: lesser tubercle of humerus
• action: medial rotation at shoulder

Question 21

what muscles are innervated by the suprascapular nerve C5?

Answer 21

supraspinatus and infraspinatus

Question 22

what muscles are innervated by the axillary nerve C5-C6?

Answer 22

deltoid and teres minor

Question 23

what muscle is innervated by the lower subscapular nerve (C5-C7)?

Answer 23

teres major

Question 24

what muscle is innervated by the (upper and lower) subscapular nerves C5-C7?

Answer 24

subscapularis

Question 25

list the 4 rotator cuff muscles

Answer 25

1. supraspinatus 2. infraspinatus 3. teres minor 4. subscapularis

Question 26

what do the rotator cuff muscles do? exception?

Answer 26

all muscles rotate humerus except supraspinatus, which initiates and assists deltoid with 1st 15 degrees of abduction of the arm

Question 27

list the 3 muscles in the anterior compartment of the arm

Answer 27

1. biceps brachii — long head and short head 2. coracobrachialis 3. brachialis

Question 28

origin, insertion and action of long head and short head of biceps brachii

Answer 28

- origin: LONG HEAD = supraglenoid tubercle of scapula, SHORT HEAD = coracoid process of scapula - insertion: tuberosity of radius and fascia of forearm via the bicipital aponeurosis - action: flexion at elbow and shoulder, supination

Question 29

origin, insertion and action of coracobrachialis

Answer 29

- origin: coracoid process of scapula - insertion: medial margin of shaft of humerus - action: adduction and flexion at shoulder

Question 30

origin, insertion and action of brachialis

Answer 30

- origin: anterior aspect of distal half of humerus - insertion: coronoid process and tuberosity of ulna - action: flexes forearm at elbow

Question 31

innervation of arm muscles in anterior compartment

Answer 31

- biceps brachii — musculocutaneous nerve C5-C6 - coracobrachialis — musculocutaneous nerve C5-C7 - brachialis — musculocutaneous nerve C5-C6 and radial nerve C7-C8

Question 32

list the muscles of the arm in the posterior compartment

Answer 32

triceps brachii — long, lateral and medial head

Question 33

what are the origins of the different heads of the triceps brachii?

Answer 33

1. long head = infraglenoid tubercle of scapula 2. lateral head = posterior shaft of humerus above spiral groove 3. medial head = posterior surface of humerus inferior to radial groove (spiral groove)

Question 34

insertion, action and innervation of triceps brachii

Answer 34

- insertion: olecranon of ulna - action: extension at elbow - innervation: radial nerve (C7-C8)

Question 35

movement at the shoulder requires action from what 3 groups of muscles?

Answer 35

- anterior axioappendicular - posterior axioappendicular - scapulohumeral