Week 4 - Upper limb + nerves

Question 1

What is special about brachioradialis?

Answer 1

It’s in the posterior compartment of the arm (lateral epicondyle) but is a flexor of the elbow

Question 2

What are the three main muscles attaching to the humerus from the medial side? What do they do?

Answer 2

Latissimus Dorsi
Pectoralis Major
Teres Major

• These are adductors and medial rotators
• Because PM is anteriorly, it is also a flexor of the shoulder joint
• Because LD and TM are posterior, they are also extensors of the shoulder joint

Question 3

What are the lateral rotators of the shoulder?

Answer 3

ONLY infraspinatus - it is the only posterior muscle that attaches on to the lateral side of the humerus

Question 4

What is the action of the deltoid?

Answer 4

It’s an abductor - it passes lateral to the shoulder joint

Question 5

Which two muscles are involved in abduction of the shoulder past ~110 degrees?

Answer 5

Trapezius and serratus anterior - these rotate the scapula upwards so the glenoid faces upwards

Question 6

Which two muscles restore a rotated upwards scapula to it’s original position?

Answer 6

Rhomboids + Pec minor`

Question 7

Which part of the scapula does pec minor act on, and in what direction?

Answer 7

Pulls the corocoid down

Question 8

What is the role of serratus anterior? What happens when it is paralysed?

Answer 8

Pulls the opposite end of the scapula downwards than that of pec minor - i.e. pec minor pulls one side, SA pulls the other.
When SA is paralysed, the medial end of the scapula is left drifting, which makes it ‘wing’ as pec minor continues to pull the lateral edge.

Question 9

Which muscles does the axillary nerve supply?

Answer 9

Deltoid and teres minor

Question 10

Which nerve feeds trapezius?

Answer 10

11th cranial nerve

Question 11

What is the antagonist muscle of the rhomboids?

Answer 11

Trapezius

Question 12

Where do the roots of the brachial plexus come from?

Answer 12

VENTRAL RAMI of spinal nerves

Question 13

Where are the roots and trunks of the BP?

Answer 13

In the neck

Question 14

Where are the cords and branches of the BP?

Answer 14

In the axilla

Question 15

How would you tell if the upper trunk of the brachial plexus was damaged?

Answer 15

UT feeds into suprascapular branch, so if it’s not working, infraspinatus is paralysed.
This causes the medial rotation of the arm and the tone of the medial rotators is much stronger - the lateral rotator has been lost.

Question 16

What is the root value of a nerve?

Answer 16

The root value of a nerve is the ventral rami from which it originates

Question 17

Which muscles of the shoulder are developmentally posterior?

Answer 17

All of them, except the pectoral

Question 18

Describe how the brachial plexus gets to the armpit

Answer 18

Extends from spinal cord, through cervicoaxillary canal in the neck, over the first rib and into the armpit

Question 19

Which structures form the M structure of the BP?

Answer 19

Musculocutaneous nerve
Lateral cord
Median nerve
Median cord
Ulnar nerve

Question 20

What makes up the upper trunk of BP?

Answer 20

C5 & C6

Question 21

WHat makes up the lower trunk of BP?

Answer 21

C8 & T1

Question 22

Which nerve innervates lats?

Answer 22

Thoracodorsal branch

Question 23

Which nerve innervates subscapularis and T major?

Answer 23

Subscapular x2

Question 24

From which cords does the long thoracic nerve come from, and what does it innervate?

Answer 24

Comes from C5, C6 and C7

Innervates serratus anterior

Question 25

What forms the posterior cord?

Answer 25

The three posterior divisions of C5, C6

Question 26

What are the posterior cord branches?

Answer 26

Thoracodorsal Axillary Radial Subscapular

Question 27

Which compartment of the arm is fed by the posterior cord?

Answer 27

The posterior/extensor

Question 28

Which compartment of the arm does the radial nerve feed?

Answer 28

The posterior compartment, because it's from the posterior cord

Question 29

Which cords feed the anterior compartment of the arm?

Answer 29

Medial and lateral cords --> flexor muscles are fed by these

Question 30

Describe the action of musculocutaneous nerve in the arm?

Answer 30

Supplies the bicep and brachialis, passing between them, then becomes lateral cutaneous nerve for the forearm

Question 31

What are the roles of the median and ulnar nerves in the arm?

Answer 31

Innervate all anterior muscles of the forearm and hand, including intrinsic hand muscles, as these are developmentally anterior

Question 32

Where is the surgical neck of the humerus and why is it called that?

Answer 32

``` Axillary nerve (posterior cord, fibres from C5 and C6) winds around the posterior side of the upper end of the humerus and enters the deltoid. A fracture in this area could cause the nerve to get trapped in the callus, weakening the deltoid/paralysing it --> surgical neck ```

Question 33

Which roots have fibres in the posterior cord?

Answer 33

ALL OF THEM

Question 34

From which roots does the median nerve have fibres?

Answer 34

All of them | Made up of branches from the anterior medial and lateral

Question 35

What does the median nerve innervate?

Answer 35

Supplies all anterior muscles of the forearm apart from FCU and 1/2 FDP Supplies thenar muscles after passing through carpal tunnel Then becomes cutaneous, supplying the anterior side of thumb and first two fingers + 1/2 ring finger

Question 36

Where does the ulnar nerve come from?

Answer 36

The lateral cord, fibres from C8 and T1

Question 37

Describe the path of ulnar nerve through the arm

Answer 37

- Moves on medial side of arm, posterior to medial epicondyle, through cubital tunnel - Straight down to wrist - At wrist, passes through tunnel at hook of hamate - Splits into deep and superficial branches

Question 38

What is the path of the median nerve down the arm?

Answer 38

With brachial artery Goes through pronator teres - is deep to FDS Emerges at wrist, goes through carpal tunnel

Question 39

What does the ulnar nerve innervate?

Answer 39

FCU and 1/2 FDP in forearm All remaining anterior muscles in the hand not fed by median nerve aka all interossei, adductor pollicis and hypothenar Also the skin of the hand on the medial side (anterior and posterior)

Question 40

Describe the course of the radial nerve through the arm

Answer 40

Crosses posterior to humerus in spiral track Moves through triceps Divides near the elbow, superficial nerve is cutaneous Deep radial passes beneath extensor muscles, running between ulna and radius Loses all fibres within the forearm

Question 41

What does the radial nerve innervate?

Answer 41

The triceps Entire posterior compartment of the forearm Deep radial also supplies posterior interosseous

Question 42

What does irritation of a nerve cause?

Answer 42

Sensory effects - altered sensation (paresthesia)/pain | Motor effects - muscle twitches

Question 43

What does total loss of nerve conduction cause?

Answer 43

Loss of sensation Weakness/paralysis of muscle Loss of movement can lead to atrophy and alteration of contour

Question 44

What's a common cause of compression or stretch of a nerve?

Answer 44

Altered bony features i.e. bony spurs, or a tumour

Question 45

What does entrapment do to a nerve?

Answer 45

Early irritation is followed by total loss of conduction

Question 46

What are phantom sensations caused by?

Answer 46

Irritation of cut nerve fibres

Question 47

How is the axillary nerve often injured?

Answer 47

At the surgical neck of the humerus

Question 48

How is the radial nerve injured?

Answer 48

At the spiral sulcus of the humerus

Question 49

How is the radial nerve injured when it's in the posterior interosseous area?

Answer 49

By fractures with dislocation - superior R-U joint

Question 50

Where are the two areas the ulnar nerve is often entrapped?

Answer 50

1. At the medial epicondyle, in the bone and fibrous arch | 2. Near the hamate bone (Guyon's canal)

Question 51

What are four effects of muscle paralysis?

Answer 51

1. Loss of movement 2. Wasting 3. Antagonist tone and limb position i.e. infraspinatus paralysis 4. Compensatory mechanisms i.e. angle for supraspinatus and abduction

Question 52

What is the axillary artery a continuation of?

Answer 52

The subclavian artery across the first rib

Question 53

What is the course of the brachial artery?

Answer 53

Down the medial side of the arm, to the cubital fossa. It then splits into radial and ulnar artery

Question 54

Where do you find the ulnar artery?

Answer 54

With the ulnar nerve in the lower 2/3 of the forearm

Question 55

Where do you find the radial artery?

Answer 55

Along the radius | Then going through the anaomical snuff box