The Brachial Plexus Flashcards Preview

ESA 2- Musculoskeletal System > The Brachial Plexus > Flashcards

Flashcards in The Brachial Plexus Deck (67):
1

What is the brachial plexus?

A network of nerve fibres that supplies the skin and musculature of the upper limb

2

Where does the brachial plexus begin?

In the root of the neck

3

Where does the brachial plexus pass?

Through the axilla, and enters the upper arm

4

What is the brachial plexus formed by?

The anterior rami (divisions) of the cervical spines C5-8, and the first thoracic spinal nerve, T1

5

What is the brachial plexus divided into to aid explanation?

Roots, trunks, divisions, cords and branches

6

What is the functional difference between the parts of the brachial plexus?

None

7

What do the roots refer to?

The beginning of the brachial plexus

8

What are the roots of the brachial plexus formed by?

The spinal nerves C5, C6, C7, C8 and T1

9

What happens at each vertebral level?

Paired spinal nerves arise

10

How do paired spinal nerves leave the spinal cord?

Via the intervertebral foramina of the vertebral column

11

What happens when the paired spinal nerves have left the spinal cord?

Each nerve divides into the anterior and posterior nerve fibres

12

How are the roots of the brachial plexus formed?

By the anterior divisions of spinal nerves C5-T1

13

What happens to the posterior divisions of the spinal nerves C5-T1?

They go on to innervate the skin and musculature of the trunk

14

What happens to the anterior division of spinal nerves C5-T1 after their formation?

They pass between the anterior and medial scalene muscles to enter the base of the neck

15

What happens at the base of the neck?

The roots of the brachial plexus converge

16

What is formed when the roots of the brachial plexus converge?

Three trunks

17

What are the trunks of the brachial plexus named based on?

Their anatomical position

18

What are the three trunks of the brachial plexus?

Superior trunk 
Middle trunk 
Inferior trunk

19

What does the superior trunk consist of?

A combination of C5 and C6 roots

20

What does the middle trunk consist of?

A continuation of C7

21

What does the inferior trunk consist of?

A combination of C8 and T1 roots

22

What happens once the trunks have been formed?

They begin to move laterally, crossing the posterior triangle of the neck

23

What happens within the posterior triangle of the neck?

Each trunk divides into two branches

24

What happens to the two branches formed from the trunks of the brachial plexus?

One division travels anteriorly (towards the front the body) and the other posteriorly (towards the back of the body)

25

What happens once the divisions have been formed?

The divisions leave the posterior triangle and pass into the axilla region

26

What happens once the anterior and posterior divisions have entered the axilla?

They combine together to form three nerves

27

How are the three nerves formed by the trunks of the brachial plexus named?

By their position relative to the axillary artery

28

What are the three cords formed from the trunks of the brachial plexus?

Lateral
Posterior
Medial

29

What is the lateral cord formed by?

The anterior division of the superior trunk 
The anterior division of the middle trunk

30

What is the posterior cord formed by?

The posterior division of the superior trunk 
The posterior division of the middle trunk
The posterior division of the inferior trunk

31

What is the medial cord formed by?

The anterior division of the inferior trunk

32

What do the cords give rise to?

The five major branches of the brachial plexus

33

Where do the cords give rise to the major branches of the brachial plexus?

In the axilla and proximal aspect of the upper limb

34

What happens to the major branches of the brachial plexus?

They continue into the upper limb to provide innervation to the muscles and skin present

35

What are the major branches of the brachial plexus?

Musculocutaneous nerve 
Axillary nerve
Radial nerve
Ulnar nerve
Median nerve

36

What is the M structure found when looking for the brachial plexus in a dissection formed by?

The musculocutaneous, median and ulnar nerves, arranged around the brachial artery

37

What does the brachial plexus have in addition to the 5 major branches?

A number of smaller nerves that arise

38

What nerves arise from the roots of the brachial plexus?

Dorsal scapular nerve
Long thoracic nerve

39

What nerves arise form the trunks of the brachial plexus?

Suprascapular 
Nerve to subclavius

40

What nerves arise from the lateral cord of the brachial plexus?

Lateral pectoral nerve

41

What nerves arise from the medial cord of the brachial plexus?

Medial pectoral nerve
Medial cutaneous nerve of arm 
Medial cutaneous nerve of forearm

42

What nerves arise from the posterior cord of the brachial plexus?

Superior subscapular nerve
Thoracodorsal nerve
Inferior subscapular nerve

43

What is an intact brachial plexus vital for?

Normal function of the upper limb

44

What are the major types of injuries that can affect the brachial plexus?

Upper brachial plexus injury 
Lower brachial plexus injury

45

What does an upper brachial plexus injury affect?

The superior roots

46

What does a lower brachial plexus injury affect?

The inferior roots

47

When does Erb’s palsy commonly occur?

Where there is excessive increase in the angle between the neck and the shoulder

48

Why does excessive increase in the angle between the neck and the shoulder result in Erb’s Palsy?

It stretches (or can tear) the nerve roots, causing damage

49

What can Erb’s Palsy occur as a result of?

Difficult birth Shoulder trauma

50

What nerves affected by Erb’s Palsy?

Nerves derived solely from C5 or C6 roots- musculocutaneous, axillary, suprascapular and nerve to subclavius

51

What muscles are paralysed in Erb’s Palsy?

Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor

52

What motor functions are lost or greatly weakened in Erb’s Palsy?

Abduction at the shoulder
Lateral rotation of the arm 
Supination of the forearm 
Flexion at shoulder

53

What sensory functions are lost in Erb’s Palsy?

Loss of sensation down lateral side of arm

54

Why is the a loss of sensation down the lateral side of the arm in Erb’s Palsy?

Because this covers the sensory innervation of the axillary and musculocutaneous nerve

55

What happens to the affected limb in Erb’s Palsy?

The affected limb hangs limply, medially rotated

56

Why is the limb medially rotated in Erb’s Palsy?

Due to the unapposed action of the pectoralis major

57

Why is the forearm pronated in Erb’s Palsy?

Due to the loss of the biceps brachii

58

What is the characteristic position of Erb’s Palsy?

‘Waiters tip’

59

What does a lower brachial plexus injury result from?

Excessive abduction of the arm

60

What is a lower brachial plexus injury called?

Klumpke Palsy

61

How does the incidence of Klumpke Palsy differ from Erb’s palsy?

It is much lower

62

What nerves are effected in Klumpke Palsy?

Those derived form the T1 root- ulna and median nerves

63

What muscles are paralysed in Klumpke Palsy?

All the small muscles of the hand

64

Why are the flexor muscles in the forearm not paralysed in Klumpke Palsy?

Although they are supplied by the ulna and median nerve, they are innervated by different roots

65

What sensory functions are lost in Klumpke Palsy?

Loss of sensation along medial side of arm

66

What is the characteristic appearance of Klumpke Palsy?

Hand has a clawed appereance

67

What gives the hand a clawed appearance in Klumpke Palsy?

The metacarpophalangeal joints are hyperextended, and the interphalangeal joints are flexed