Shoulder muscles

Question 1

trapezius

Answer 1

superficial muscle

origin:
- superior nuchal line
- occipital protuberance
- spinous processes of C7-T12

insertion:
- clavicle
- acromion
- spine of scapula

innervation:
- accessory nerve (CN11)

action:
- superior: elevates
- inferior: depresses
- middle part (or all parts together): retracts scapula

Question 2

deltoid

Answer 2

superior muscles

origin:
- inferior spine of scapula
- lateral margins of acromion
- anterior border of lateral clavicle

insertion:
- deltoid tuberosity of humerus

innervation:
- axillary nerve (C5, C6)

action:
- anterior part: flexes and medially rotates arm
- middle part: abducts arm
- posterior part: extends and laterally rotates arm

Question 3

levator scapulae

Answer 3

superior muscles

origin:
- transverse processes of C1-C4

insertion:
- superior angle of scapula

innervation:
- dorsal scapular (C5)
- cervical (C3, C4)

action:
- elevates scapula and tilts its glenoid cavity inferiorly by rotating the scapula

Question 4

rhomboid minor

Answer 4

superior muscles

origin:
- spinous processes of C7 and T1

insertion:
- medial border of scapula above scapular spine

innervation: dorsal scapular nerve (C4, C5)

action:
- retract scapula and rotate it to depress glenoid cavity
- fix scapula to thoracic wall

Question 5

rhomboid major

Answer 5

superior muscles

origin:
- spinous processes of T2-T5

insertion:
- medial border of scapula below scapular spine

innervation:
- dorsal scapular nerve (C4, C5)

action:
- retract scapula and rotate it to depress glenoid cavity
- fix scapula to thoracic wall

Question 6

supraspinatus

Answer 6

posterior region

origin:
- supraspinatus fossa of scapula

insertion:
- greater tubercle of humerus

innervation:
- suprascapular nerve (C5,C6)

main action:
- arm abduction / rotator cuff

Question 7

infraspinatus

Answer 7

posterior region

origin:
- infraspinous fossa of scapula

insertion:
- greater tubercle of humerus

innervation:
- suprascapular nerve (C5, C6)

main action:
- laterally rotate arm / rotator cuff

Question 8

teres minor

Answer 8

posterior region

origin:
- lateral border of scapula

insertion:
- greater tubercle of humerus

innervation:
- axillar nerve (C5, C6)

main action:
- laterally rotate arm / rotator cuff

Question 9

teres major

Answer 9

posterior region

origin:
- inferior angle of scapula

insertion:
- intertubercular groove of humerus

innervation:
- lower subscapular nerve (C5,C6)

main action:
- extension, adduction, and internal rotation of arm

Question 10

long head of triceps

Answer 10

posterior region

origin:
- infra-glenoid tubercle on scapula

insertion:
- olecranon of the ulna

innervation:
- radial nerve (C6-C8)

main action:
- extension of the elbow
- adduction of the shoulder
- extension of the arm

Question 11

pectoralis major - clavicular head

Answer 11

axilla

origin:
- anterior surface of clavicle

insertion
- lateral lip of intertubercular sulcus of humerus

innervation:
medial and lateral pectoral nerves (C5, C6)

action:
- flexion, adduction and medial rotation of the arm

Question 12

pectoralis major - sternocostal head

Answer 12

axilla

origin:
- anterior surface of sternum
- first 7 costal cartilages

insertion
- lateral lip of intertubercular sulcus of humerus

innervation
- C7 to T1 spinal nerves

action
- flexion, adduction and medial rotation of arm

Question 13

subclavius

Answer 13

axilla

origin:
- first rib and its costal cartilage

insertion:
- middle one-third of clavicle

innervation:
- nerve to subclavius (C5 and C6)

action:
- depresses the clavicle down forward

Question 14

pectoralis minor

Answer 14

axilla

origin:
- ribs 3-5

insertion:
- coracoid process of scapula

innervation:
- medial pectoral nerve (C8-T1)

action:
- elevates the ribs and draws the scapula down and medially

Question 15

serratus anterior

Answer 15

medial wall of axilla

origin:
- 1-9 ribs

insertion:
- costal surface of medial border of scapula

innervation:
- long thoracic nerve (C5-C7)

action:
- protraction and rotation of the scapula

Question 16

subscapularis

Answer 16

posterior wall of axilla

origin:
- subscapular fossa

insertion:
- lesser tubercle of humerus

innervation:
- upper and lower subscapular nerve (C5 & C6)

action:
- medially rotates and adduct arm - rotator cuff

Question 17

latissimus dorsi

Answer 17

posterior wall of axilla

origin:
- spinous processes of T7-L1 thoracolumbar fascia
- iliac crest
- inferior 3 or 4 ribs

insertion:
- intertubercular groove of humerus
- inferior angle of the scapula

innervation:
- thoracodorsal nerve (C6-C8)

action:
- adducts, extends, medially rotates humerus