Extrinsic Muscles of the Shoulder

Question 1

List the extrinsic muscles of the shoulder

Answer 1

1. Trapezius
2. Latissimus dorsi
3. Levator scapulae
4. Rhomboideus minor
5. Rhomboideus major

Question 2

Origin of the Trapezium (3)

Answer 2

1. Back of skull - (a) Medial 1/3 of superior nuchal line
   (b) External occipital protuberance
2. Back of neck - (a) Ligamentum nuchae
   (b) spine of C7
3. Back of thorax - all thoracic spines and supraspinous ligaments

Question 3

Insertion of the trapezium (3)

Answer 3

1. Upper fibres (occipital and upper cervical) - Posterior aspect of lateral 1/3 of clavicle
2. Middle fibres (lower cervical and upper thoracic) - Medial border of acromion and upper lip of the crest of spine of scapula
3. Lower fibres - Ascend to be inserted by a tendon into the tubercle of the crest of spine of scapula

Question 4

Nerve supply of trapezium

Answer 4

1. Motor - Spinal accessory nerve
2. Sensory (proprioceptive) - branches from C3,C4

Question 5

Actions of trapezium

Answer 5

1. Upper fibres - Elevates scapula and shoulder (shrug shoulder)
2. Middle fibres - Retracts scapula (standing to attention of soldiers)
3. Lower fibres - Rotates scapula so that glenoid cavity faces upwards
4. Acting from insertion, trapezius pulls head backwards and laterally

Question 6

Deep relations of trapezium

Answer 6

Rest of muscles of the back + artery + nerve
1. Levator scapulae
2. Rhomboids
3. Latissimus dorsi
4. Supraspinatus
5. Infraspinatus
6. Spinal accessory nerve
7. Superficial branch of transverse cervical artery

Question 7

Origin of latissimus dorsi (5)

Answer 7

by an aponeurosis from:

1. lower 6 thoracic spines and supra spinous ligaments (undercover trapezius)
2. from lumbar spines (through thoracolumbar fascia)
3. posterior part of outer lip of iliac crest
4. outer surfaces of lower 3 or 4 ribs
5. dorsal aspect of inferior angle of the scapula

Question 8

Insertion of latissimus dorsi

Answer 8

By a flat tendon into the floor of the bicipital groove of humerus

Question 9

Nerve supply of latissimus dorsi

Answer 9

Nerve to latissimus dorsi (throracodorsal nerve) from posterior cord of brachial plexus

enters with thoracodorsal artery

Question 10

Actions of latissimus dorsi

Answer 10

1. Extension, adduction and medial rotation of arm
2. Pulls whole shoulder girdle downwards and backwards (as in swimming)
3. Can pull trunk upwards when arms are fixed above the head (as in climbing)
4. Strong muscle of expiration as it can compress lower part of thoracic cage

Question 11

Relation of latissimus dorsi with teres major

Answer 11

triple relation
1. first behind
2. second below it
3. finally infront of it at its insertion

Question 12

Origin of levator scapulae

Answer 12

Upper 4 cervical transverse processes

Question 13

Insertion of levator scapulae

Answer 13

Dorsal aspect of medial border of scapula extending from superior angle to the root of the spine

Question 14

Nerve supply of levator scapulae

Answer 14

1. C3, C4 (from cervical plexus)
2. Nerve to rhomboids (C5): from brachial plexus

Question 15

Actions of elevator scapulae

Answer 15

1. Elevates the scapula and fixes it
2. Rotates the scapula downwards
3. Lateral flexor of the neck (when scapula is fixed)

Question 16

Origin of rhomboideus minor

Answer 16

lower part of ligament nuchae and spines of C7 and T1

Question 17

Insertion of rhomboideus minor

Answer 17

dorsal aspect of medial border of scapula opposite the root of spine

Question 18

Origin of rhomboideus major

Answer 18

spines of the 2nd, 3rd, 4th and 5th thoracic vertebrae and supraspinous ligaments

Question 19

Insertion of rhomboideus major

Answer 19

dorsal aspect of medial border of scapula extending from the root of spine to the inferior angle

Question 20

Nerve supply of the 2 rhomboids

Answer 20

Nerve to rhomboids (dorsal scapular nerve) from C5

Question 21

Actions of rhomboids

Answer 21

1. retraction of scapula
2. downward rotation of scapula