Innervation of the Upper Limb

Question 1

Which ventral rami form the brachial plexus?

Answer 1

C5-T1

Question 2

What type of fibres are contained within the brachial plexus?

Answer 2

Sympathetic postganglionic, sensory and somatic.

Question 3

Name the separate parts of the brachial plexus.

Answer 3

Roots –> trunks –> divisions –> cords –> branches.

Question 4

What are the roots of the brachial plexus?

Answer 4

C5-T1

Question 5

What are the trunks of the brachial plexus, and what roots form them?

Answer 5

Superior (C5+C6), Middle (C7) and Inferior (C8+T1)

Question 6

What are the divisions of the brachial plexus?

Answer 6

Anterior and posterior from each cord. Nerves from anterior division innervate flexors + overlying skin. Nerves from posterior division innervate extensors + overlying skin.

Question 7

Why are the cords named how they are?

Answer 7

Due to their relative position to the axillary artery

Question 8

What are the cords of the brachial plexus, and what do they consists of?

Answer 8

Lateral (anterior divisions of superior and middle trunk), posterior (posterior divisions of all trunk) and medial (anterior divisions of inferior trunk).

Question 9

What are the branches of the brachial plexus that innervate the upper limb?

Answer 9

Axillary and radial nerves (from posterior cord), musculocutaneous (from lateral cord), ulnar nerve (from medial cord) and median nerve (from both lateral and medial cords).

Question 10

What part of the nervous system does NOT innervate the limbs?

Answer 10

Parasympathetic.

Question 11

What sympathetic nerves travel in the brachial plexus?

Answer 11

Post-ganglionic

Question 12

What do post-ganglionic sympathetic fibres innervate?

Answer 12

Arrector Pili muscles, sweat glands and blood vessels.

Question 13

What 2 parts of the upper limb does the SNS NOT innervate

Answer 13

Cartilage and Nail.

Question 14

What are the scores of the MRC grading scale?

Answer 14

0 - no movement
1 - belly of muscle moves
2 - moves without gravity
3- moves against gravity
4- against gravity + resistance
5 - full strength.

Question 15

Identify myotome and reflexes fro C5, C6, C7, C8 and T1.

Answer 15

C5 - Deltoid - Biceps Reflex.
C6 - Wrist Extensors - brachioradialis reflex
C7 - Triceps - Triceps reflex
C8 - Finger flexors - finger flexor reflex
T1 - Finger abductors/adductors - no reflex.

Question 16

When considering single spinal nerve injury, what should be assessed?

Answer 16

Dermatome, myotome and reflex.

Question 17

What are the root values of the axillary nerves, and what does it innervate?

Answer 17

C5C6. Innervates deltoid and teres minor, the shoulder joint and skin over deltoid.

Question 18

What are the root values of the radial nerve, and what does it innervate?

Answer 18

C5-T1. Innervates muscles in the posterior arm and forearm and skin overlying it. (+skin on dorsum of hand)

Question 19

When the radial nerve splits, which nerves are formed and what do they innervate?

Answer 19

Posterior interosseous nerve (deep) supplies extensor muscles of forearm.
Superficial branch of radial nerve - innervates skin on dorsum of hand.

Question 20

What are the root values of the musculocutaneous nerve, and what does it innervate?

Answer 20

C5-C7. innervates muscles in the anterior compartment of the arm.

Question 21

how does the musculocutaneous nerve terminate?

Answer 21

As the lateral cutaneous nerve of the forearm.

Question 22

Name the 6 additional nerves from the brachial plexus

Answer 22

Dorsal Scapular (C5), long thoracic (c567), suprascapular (sup. trunk), subscapular (post. cord), thoracodorsal (post cord), Medial/lateral pectoral nerves (med/lat cords)

Question 23

What does the following nerve innervate. Dorsal scapular

Answer 23

Rhomboid major + minor, Levator scapulae.

Question 24

What does the following nerve innervate. Long thoracic.

Answer 24

Serratus anterior.

Question 25

What does the following nerve innervate. Suprascapular.

Answer 25

Supraspinatus + infraspinatus

Question 26

What does the following nerve innervate. Subscapular.

Answer 26

Subscapularis + teres major

Question 27

What does the following nerve innervate. Thoracodorsal

Answer 27

Latissimus dorsi

Question 28

What does the following nerve innervate. Pectoral nerves

Answer 28

Pectoralis Major + Minor.

Question 29

What are the root values of the ulnar nerve?

Answer 29

C8-T1 (can be worked out from plexus). Comes from the medial cord of the brachial plexus.

Question 30

Where does the ulnar nerve run?

Answer 30

Medial to brachial artery, behind medial epicondyle of humerus, into medial side of forearm. Lies with ulnar artery at the wrist and passes over flexor retinaculum to enter the hand.

Question 31

Where it the ulnar nerve most vulnerable to damage?

Answer 31

Behind medial epicondyle and wrist.

Question 32

Which structures does the ulnar nerve innervate?

Answer 32

Flexor carpi ulnaris, medial 1/2 of flexor digitorum profundus, hypothenar, interossei and medial lumbrical muscles. Skin over medial aspect of hand and medial 1.5 fingers.

Question 33

What are the root values of the median nerve?

Answer 33

C5-T1. (remember, the only root values that cannot be worked out from the brachial plexus is axillary nerve C5-C6.)

Question 34

Where in the brachial plexus does the median nerve arise?

Answer 34

Medial and lateral cords

Question 35

Where does the median nerve run?

Answer 35

Medial to brachial artery at cubital fossa, deep into the forearm before it becomes superficial to pass through the carpal tunnel. Vulnerable to injury at the wrist.

Question 36

Which structures does the median nerve innervate?

Answer 36

Palmaris longus, flexor carpi radialis, flexor digitorum, thenar and lateral lumbricals, flexor pollicis longus, flexor digitorum profundus (lateral 1/2) and pronator quadratus.
Also skin of lateral hand + 3.5 digits.