MSK Session 3- Back And Shoulder Muscles, And The Shoulder Joint

Question 0

What are the three groups of extrinsic back muscles?

Answer 0

• superficial
• deep
• scapulo-humeral

Question 1

What are intrinsic back muscles responsible for?

Answer 1

Posture

Question 2

What are the two superficial back muscles?

Answer 2

Trapezius

Latissimus dorsi

Question 3

What are the 2 deep back muscles?

Answer 3

Levator scapulae

Rhomboids

Question 4

What are the 2 scapulo-humeral muscles?

Answer 4

Teres major

Deltoid

Question 5

What is the action of each of the parts of the trapezius?

Answer 5

• descending/superior fibres- elevate and rotate the scapula
• middle fibres- retract the scapula
• ascending/inferior fibres- depress the scapula
• abduction past 90 degrees

Question 6

What is the innervation of the trapezius muscle?

Answer 6

Spinal accessory nerve

Question 7

What is the action of the latissimus dorsi?

Answer 7

Extension, adduction and medial rotation of the upper limb.

Question 8

What is the innervation of the latissimus dorsi?

Answer 8

Thoracodosral nerve

Question 9

What is the action of the Levator scapulae muscle?

Answer 9

Elevates the scapula

Question 10

What is the innervation to the Levator scapulae?

Answer 10

Dorsal scapula nerve

Question 11

What is the action of the rhomboids?

Answer 11

Retraction and rotation of the scapula.

Question 12

What is the innervation to the rhomboids?

Answer 12

Dorsal scapula nerve

Question 13

Which rhomboid is most superior?

Answer 13

Minor

Question 14

What is the action of the the three deltoid segments?

Answer 14

• anterior/clavicular fibres- flexion of the arm
• middle/acromial fibres - abduction of the arm between 15 and 90 degrees.
• posterior/spinal fibres - extension of the arm

Question 15

What is the innervation to the deltoid muscle?

Answer 15

Axillary nerve

Question 16

What is the action of teres major?

Answer 16

Adduction and medial rotation of the arm.

Question 17

What is the innervation to teres major?

Answer 17

Lower subscapular nerve

Question 18

What are the four rotator cuff muscles?

Answer 18

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

Question 19

What is the general function of the rotator cuff muscles?

Answer 19

Support and stabilise the shoulder joint.

Question 20

What is the action and innervation of supraspinatus?

Answer 20

Abduction up to 15 degrees

Innervation is the suprascapular nerve

Question 21

What is the action and innervation of infraspinatus?

Answer 21

Lateral arm rotation.

Innervation- suprascapular nerve

Question 22

What is the action and innervation of teres minor?

Answer 22

Action- lateral rotation and weak adduction

Innervation- axillary nerve

Question 23

What is the action and innervation of subscapularis?

Answer 23

Action- medial rotation.

Innervation- upper and lower subscapular nerve

Question 24

What is the articulation of the shoulder joint?

Answer 24

The head of the humerus sits in the glenoid cavity, which is deepened by the glenoid labrum.

Question 25

What type of joint is the shoulder joint?

Answer 25

A ball and socket synovial joint

Question 26

Why is the shoulder joint unstable and commonly dislocated? (4)

Answer 26

- the glenoid cavity is shallow - the movements of the joint are multi planar - the capsule is lax - the articulating surfaces are disproportionate.

Question 27

How is stability of the shoulder joint achieved? (4)

Answer 27

- rotator cuff muscles - other muscles - ligaments - capsule

Question 28

Which way does the shoulder joint most commonly dislocate and why?

Answer 28

Inferiorly and anteriorly. Because the inferior part of the capsule is the weakest as it is not reinforced by ligaments or the rotator cuff muscles.

Question 29

What is the shoulder joint capsule?

Answer 29

A loose, fibrous layer.

Question 30

Why is the capsule lax?

Answer 30

To allow full abduction of the arm

Question 31

What are the five ligaments of the shoulder joint?

Answer 31

- glenohumeral- there are three of them (superior, middle and inferior) that move inferolaterally from the glenoid labrum-> humerus. - coraco-acromial - between the acromion and coracoid process - coraco-humeral - between the coracoid process and the greater tubercle - transverse humeral - holds the long head of the biceps tendon in place during movement - coraco-acromial arch - prevents upper displacement of the humeral head.

Question 32

How is shoulder dislocation caused? (2)

Answer 32

- by excessive extension and lateral rotation | - trauma to a fully abducted arm

Question 33

Which nerve can be injured during shoulder dislocation? What are the consequences?

Answer 33

The axillary nerve | Paralysis of the deltoid muscle and loss of sensation over the regimental patch area.

Question 34

What is painful arc syndrome?

Answer 34

It is when the supraspinatous tendon rubs under to the coraco-acromial arch, causing irritation and inflammation of the tendon and subacromial bursa.

Question 35

In painful arc syndrome, when is pain felt worst?

Answer 35

During 50-130 degree abduction