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Neuroanatomy > Innervation of the Upper Limb > Flashcards

Innervation of the Upper Limb Flashcards

1
Q

What are the 6 regions of the upper limb?

A
  • shoulder
  • arm
  • elbow
  • forearm
  • wrist
  • hand
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2
Q

What are the major functions of the upper limb?

A
  • grasping movements
  • position hands for use as a mechanical and sensory tool
  • aids in communication
  • assists in locomotion, balancing and swinging
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3
Q

Why is the thumb the most important finger?

A

it is responsible for 50% of hand function

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4
Q

What are the joints and bones of the shoulder?

A

glenohumeral ball and socket joint made up of the scapula and humerus

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5
Q

What is the bone of the arm?

A

humerus

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6
Q

What are the 3 bones of the elbow joint?

A

distal humerus, lateral radius and medial ulna

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7
Q

What are the 3 bones of the wrist joint?

A

radius, ulnar and carpal

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8
Q

What are the 2 bones of the forearm?

A

radius and ulna

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9
Q

What are the 3 joints of the hand?

A

MCM, PIP and DIP

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10
Q

What are the 3 bones of the hand?

A

carpals, metacarpals and phalanges

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11
Q

Where is the PIP?

A

between the proximal and medial phalanges

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12
Q

What are the 3 movement types of the upper limb?

A

flexion, extension and circumduction

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13
Q

What is abduction and adduction of the hand?

A
  • abduction = moving away from the midline
  • adduction = moving towards the midline
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14
Q

What are the movements of the elbow joint?

A

flexion and extension

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15
Q

What are the movements of the radio-ulnar joints?

A

pronation and supination

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16
Q

What are the movements of the wrist joints?

A

flexion, extension, abudction and circumduction

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17
Q

What are the movements of the MCP joints?

A

flexion, extension, abudction and circumduction

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18
Q

What are the movements of the PIP and DIP joints?

A

flexion and extension

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19
Q

What do the interior and exterior compartments of the forearm do?

A
  • interior = flexion
  • exterior = extension
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20
Q

What is the biggest muscle of the shoulder?

A

deltoid

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21
Q

What are the rotator cuff muscles?

A

the 4 muscles that surround and stabilise the shoulder joint

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22
Q

What is the brachial plexus?

A

a network of nerves in the shoulder that carries movement and sensory signals from the spinal cord to the arms and hands

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23
Q

Where do brachial plexus injuries typically stem from and what can they cause?

A

trauma to the neck, and can cause pain, weakness and numbness in the arm and hand

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24
Q

What is the brachial plexus formed of and what is it closely related to?

A

the ventral rami of C5 to T1 spinal nerves and is closely related to the axillary artery and vein

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25
Q

Why are the brachial plexus nerves prone to injuries?

A

they travel a long distance

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26
Q

What are the 5 parts of the brachial plexus?

A
  • roots (neck)
  • trunks (neck)
  • divisions (behind clavicle)
  • cords (in the axilla/armpit)
  • terminal branches/nerves
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27
Q

What are the 3 cords of the brachial plexus?

A

lateral, medial and posterior cords

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28
Q

What are the 5 terminal branches of the brachial plexus?

A
  • musculocutaneous nerve
  • axillary nerve
  • median nerve
  • ulnar nerve
  • radial nerve
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29
Q

What is the musculocutaneous nerve?

A

branch of the lateral cord of the brachial plexus (C5-C7)

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30
Q

Describe the pathway of the musculocutaneous nerve

A
  • it travels distally and punctures the coracobrachialis muscle
  • it then travels down to the lateral side and becomes the lateral cutaneous of the forearm
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31
Q

Where does the musculocutaneous nerve supply motor function?

A
  • coracobrachialis (middle)
  • biceps brachii (top)
  • brachialis muscles (bottom)
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32
Q

What does cutaneous mean?

A

close to the skin

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33
Q

Where does the musculocutaneous nerve supply sensory function?

A

the lateral skin of the forearm

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34
Q

What would happen if the musculocutaneous nerve was cut?

A

the coracobrachialis muscle would not function, and the shoulder and elbow would not be able to flex as well as sensory loss of the forearm

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35
Q

What is the biceps reflex?

A

a deep tendon reflex test that examines the function of the C5 and the C6 reflex arcs

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36
Q

What is the insertion point of the bicep?

A

the tendon

37
Q

What are the outcomes of the bicep reflex?

A

contraction of the bicep and relaxation of the tricep

38
Q

Where does the axillary nerve arise from?

A

the posterior cord of the brachial plexus (C5-C6)

39
Q

What is the pathway of the axillary nerve?

A
  • it exits the axilla posteriorly and passes posteriorly around the surgical neck of the humerus
  • it then becomes the radial nerve and goes behind the humerus to supply the motor function to the deltoid and teres minor muscles
40
Q

Where does the axillary nerve supply sensory function?

A

to the skin over the deltoid via the superior lateral cutaneous nerve of the arm

41
Q

What would a fracture of the surgical neck of the humerus do?

A

injure the axillary nerve which results in paralysis of the deltoid and weakness of abduction of the arm and sensory loss of the skin over the deltoid (regimental badge area)

42
Q

What does the median nerve arise from?

A

a branch from the lateral cord and a branch from the medial cord of the brachial plexus (C5-T1)

43
Q

What is the pathway of the median nerve?

A

it extends from the terminal branches of the brachial plexus distally to the hand

44
Q

Where does the median nerve supply motor function?

A

the anterior compartment of the forearm for flexion of the wrist joint and is important for gripping

45
Q

Where is the median nerve located at the cubital fossa (elbow region)?

A

anterior to the brachialis muscle and medial to the brachial artery

46
Q

What are the 3 layers of the anterior compartment of the forearm and what are they responsible for?

A
  1. superficial layer – flexion (wrist joint) and pronation (radio-ulnar joint)
  2. intermediate layer – flexion (wrist joint and MCP, DIP, PIP joints)
  3. deep layer – flexion (wrist joint and MCP, DIP, PIP joints)
47
Q

Where do the intermediate and deep layers of the anterior compartment of the forearm travel?

A

all the way down to the tips of the fingers but not the thumb

48
Q

How is muscle attached to bone?

A

via tendons (fibrous connective tissue)

49
Q

What does the median nerve allow?

A

pronation of the forearm

50
Q

What supplies the lateral part of the deep layer?

A

the median nerve (the medial half is supplied by the ulnar nerve)

51
Q

What muscles does the median nerve supply?

A

pronator teres, FDS and FPL

52
Q

How does the median nerve enter the hand?

A

by passing through the carpal tunnel, deep to the flexor retinaculum

53
Q

What is the carpal tunnel?

A

a fibro-osseous tunnel, formed by the flexor retinaculum and the wrist bones

54
Q

What causes carpal tunnel syndrome?

A

tendon inflammation which compresses the median nerve in the carpal tunnel

55
Q

How does the median nerve supply the motor function to the thumb?

A

via the thenar muscles

56
Q

What are the 3 thenar muscles?

A
  • abductor pollicis brevis
  • flexor pollicis brevis
  • opponens pollicis
57
Q

Where does the median nerve supply sensory function?

A

the lateral part of the palm and the palmar surface of the lateral 3½ digits (including nailbeds)

58
Q

What can injury to the median nerve be caused by?

A

a fracture of the distal humerus

59
Q

What does injury to the median nerve result in?

A

being unable to form a fist and producing the ‘Hand of Benedict’ sign due to reduced impairment of flexion of the 2nd and 3rd fingers

60
Q

What are symptoms of carpal tunnel syndrome?

A
  • weakness of abduction, flexion and opposition of thumb
  • sensory loss over the palmar surface of the lateral 3½ digits
61
Q

What is the ulnar nerve?

A

a branch of the medial cord of the brachial plexus (C7-T1)

62
Q

What is the pathway of the ulnar nerve?

A
  • it travels down medial to the axillary artery and goes behind the medial epicondyle but has no branches in the arm
  • it then passes into the medial side of the forearm, and supplies1½ muscles in the forearm
63
Q

What happens when the FCU contracts?

A

flexion of the wrist

64
Q

What is the 1 muscle valley of the intermediate layer?

A

FDS supplied by the median nerve

65
Q

How does the ulnar nerve enter the hand?

A

by passing above the carpal tunnel, superficial to flexor retinaculum at the wrist

66
Q

Why is the ulnar nerve prone to injury?

A

it is very close to the skin

67
Q

Where does the ulnar nerve supply motor function to?

A

one muscle of the thumb and most of the muscles in the other fingers (muscles of the hypothenar eminence)

68
Q

What are the muscles of the hypothenar eminence?

A
  • abductor digiti minimi
  • flexor digiti minimi brevis
  • opponens digiti minimi
69
Q

What is the function of the muscles of the hypothenar eminence?

A

to abduct and flex the 5th finger and to allow opposition

70
Q

What is injury to the ulnar nerve commonly caused by?

A

a fracture of the medial epicondyle

71
Q

Where is the ulnar nerve susceptible to compression?

A

at the elbow or the wrist, which results in a “claw hand”

72
Q

What does the extent of the claw hand after injury to the ulnar nerve depend on?

A

muscles in the forearm; the FDS and FDP are still extending to the fingers and pulling them down

73
Q

What happens if the injury to the ulnar nerve is more proximal?

A

both the lumbrical and forearm muscles do not work, and the ‘claw’ is less obvious

74
Q

What does a proximal injury to the ulnar nerve lead to?

A

loss of adduction of the thumb because of paralysis of the adductor pollicis muscle as well as sensory loss over the medial part of the hand and medial 1½ fingers

75
Q

What are the medial 2 lumbar muscles supplied by and what are they responsible for?

A

the ulnar nerve and are responsible for the movement of bending and extending the fingers (flex at MCP and extend at PIP and DIP)

76
Q

What is the longest nerve in the upper limb?

A

the radial nerve

77
Q

Why is the radial nerve most commonly injured?

A

due to its long and tortuous course and its proximity to the humeral shaft

78
Q

Where does the radial nerve arise from?

A

the posterior cord of the brachial plexus (C5-T1)

79
Q

What is the pathway of the radial nerve?

A

it descends posteriorly to the axillary artery between the three heads of the triceps branchii muscle

80
Q

Which muscle does the radial nerve supply motor function to?

A

the extensor at the elbow joint

81
Q

What does the radial nerve do on the lateral side of the arm?

A

enter the anterior compartment of the arm, between the brachialis and brachioradialis muscles and supplies the brachioradialis muscle (functions to stabilise elbow during flexion).

82
Q

What is the triceps reflex?

A

a reflex that elicits involuntary contraction of the triceps brachii muscle and is sensed and transmitted by the radial nerve used to test the C7 and C8 spinal nerves

83
Q

What happens to the radial nerve after it enters into the forearm?

A

it travels distally and divides into deep (motor) and superficial (sensory) branches

84
Q

What is the deep branch of the radial nerve responsible for?

A

extension of the wrist and fingers (‘talk to the hand’, stop)

85
Q

Where is the deep branch of the radial nerve located?

A

between the extensor muscles of the back of the forearm

86
Q

Where does the radial nerve supply sensory function?

A
  • the skin on the posterior surface of the arm via the posterior cutaneous and inferior lateral cutaneous nerve (arises in the axilla)
  • the skin of the lateral side of the back of the hand, and the back of the lateral 3½ digits (excluding nailbeds)
87
Q

Where does the superficial branch of the radial nerve descend?

A

on the anterolateral aspect of the forearm under the brachioradialis muscle then ~2/3 of the way down the forearm, it passes dorsally to the back of the hand

88
Q

What is the effect of injury to the radial nerve in the axilla?

A

“Crutch palsy”; the inability to extend the elbow

89
Q

What is the effect of injury to the radial nerve in the spiral groove?

A

“Saturday night palsy”; the inability to extend the wrist (wrist drop)

Neuroanatomy (17 decks)

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