S8: the upper limb (1)

Question 1

List the 4 joints of the shoulder girdle

Answer 1

Glenohumeral joint
Sternoclavicular joint
Acromioclavicular joint
Scapulothoracic joint (not actually a true joint)

Question 2

Describe the shoulder joint

Answer 2

Most mobile joint in the body
Ball and socket joint
Articulation between the humeral head and glenoid fossa

Question 3

What factors stabilise the shoulder joint?

Answer 3

Glenoid labrum = deepens the socket & reduces the risk of dislocation
Rotator cuff muscles (however, inferior aspect has not reinforcement)
Glenohumeral ligaments – superior, meddle & inferior -> act to reduce the risk of anterior dislocation
Other ligaments include = coracoclavicular ligament, transverse humeral ligament, coraco-acromial ligament, coracohumeral ligament

Question 4

Describe the quadrangular space

Answer 4

Superior border = inferior margin of teres minor
Inferior border = superior margin of teres major
Medial border = long head of triceps brachii
Lateral border = surgical neck of humerus
Clinical importance: the route via which the axillary nerve and posterior circumflex humeral artery enter the posterior compartment of the arm

Question 5

Describe the triangular space

Answer 5

Superior border = inferior margin of teres minor
Inferior border = superior margin of teres major
Lateral border = long head of triceps brachii
Passageway through which the circumflex scapular vessels enter the infraspinatus fossa

Question 6

Describe the triangular interval

Answer 6

Superior border = inferior margin of teres major
Medial border = long head of triceps brachii
Lateral border = shaft of humerus/lateral head of triceps brachii
Radial nerve & profunda brachii artery are visible in the base of the triangular interval as they wind around the humerus in the radial groove

Question 7

Describe the two bursae around the shoulder joint

Answer 7

Subacromial bursa = under the acromion
-acts like a cushion, reducing friction as the supraspinatus tendon passes under structures
Subscapular bursa = between the tendon of subscapularis & neck of the scapula
-protects the tendon of subscapularis muscle

Question 8

Describe the subacromial space

Answer 8

Space between the coraco-acromial arch & head of the humerus
Contents = subacromial bursa, supraspinatus tendon, joint capsule & long head of biceps

Question 9

List the extrinsic muscles of the shoulder

Answer 9

Superficial: trapezius & latissimus dorsi
Deep: levator scapulae, rhomboid major, rhomboid minor

Question 10

List the intrinsic muscles of the shoulder

Answer 10

Deltoid, teres major & rotator cuff muscles

Rotator cuff muscles: supraspinatus, infraspinatus, subscapularis & teres minor (SITS)

Question 11

Name the origins, insertions, actions, and innervations of the superficial extrinsic shoulder muscles

Answer 11

Trapezius = origin: external occipital protuberance of the skull, the nuchal ligament & spinous processes of C7-T12, insertion: clavicle, acromion & spine of scapula, innervation: spinal accessory nerve/receives fibres from the C3/C4 spinal nerves
Actions: upper fibres – elevate scapula & rotate it during abduction of the arm above 90 degrees, middle fibres – retract the scapula, lower fibres – pull the scapula inferiorly
Latissimus dorsi = origin: spinous processes of T6-T12, iliac crest, thoracolumbar fascia & inferior three ribs, insertion: intertubercular sulcus of humerus, innervation: thoracodorsal nerve
Actions: extension, adduction & medial rotation of upper limb

Question 12

Name the origins, insertions, actions, and innervations of the deep extrinsic shoulder muscles

Answer 12

Insertion = medial border of the scapula
Innervation = dorsal scapular nerve
Action of rhomboids = retraction of scapula & rotation of the medial border -> glenoid fossa rotated inferiorly
Levator scapulae = origin: transverse processes of the C1-C4 vertebrae, action: elevates the scapula
Rhomboid minor = origin: spinous processes of C7-T1 vertebrae
Rhomboid major = origin: spinous processes of T2-T5 vertebrae

Question 13

Name the origins, insertions, actions, and innervations of the intrinsic shoulder muscles (excluding rotator cuff muscles)

Answer 13

Deltoid = origin: anterior border & upper surface of the lateral third of the clavicle, from the acromion & spine of the scapula, insertion: deltoid tuberosity on humerus, innervation: axillary nerve
Actions: anterior fibres – flexion/medial rotation of arm, middle fibres – abduction of arm from 15 to 90 degrees, posterior fibres – extension/lateral rotation of arm
Teres major = origin: posterior surface of the inferior angle of the scapula, insertion: medial lip of the intertubercular groove of humerus, innervation: lower subscapular nerve
Actions: adduction & medial rotation

Question 14

Name the origins, insertions, actions, and innervations of the rotator cuff muscles

Answer 14

Subscapularis = origin: subscapular fossa, insertion: lesser tubercle of humerus, innervation: upper/lower subscapular nerve, action: medial rotation
Supraspinatus = origin: supraspinous fossa, insertion: greater tubercle of humerus, innervation: suprascapular nerve, action: abduction of arm from 0-15 degrees
Infraspinatus = origin: infraspinatus fossa, insertion: greater tubercle of humerus, innervation: suprascapular nerve, action: lateral rotation
Teres minor = origin: posterior surface of scapula, insertion: greater tubercle of humerus, innervation: axillary nerve, action: lateral rotation

Question 15

Name the origins, insertions, actions, and innervations of the anterior arm

Answer 15

BBC
Innervation: musculocutaneous nerve
Biceps brachii = origin: short head – coracoid process of scapula & long head – supraglenoid tubercle of scapula, insertion: radial tuberosity, action: flexion & supination
Brachialis = origin: anterior surface of the distal half of the humeral shaft, insertion: coronoid process of the ulna & ulnar tuberosity, innervation: contributions from radial nerve, action: flexion only at elbow
Coracobrachialis = origin: coracoid process of scapula, insertion: medial side of humeral shaft, action: flexion & weak adduction

Question 16

Name the origins, insertions, actions, and innervations of the posterior arm

Answer 16

Triceps brachii 
Origin: long head – infraglenoid tubercle, lateral head – shaft of humerus, superior to radial groove & medial head – shaft of humerus, inferior to radial groove 
Insertion: olecranon of ulna 
Innervation: radial nerve
Action: extension of forearm at elbow