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ESA 2- Musculoskeletal System > Muscles of the Posterior Forearm > Flashcards

Muscles of the Posterior Forearm Flashcards

1
Q

What are the muscles in the posterior compartment of the forearm commonly known as?

A

The extensor muscles

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2
Q

What is the general function of the muscles of the posterior compartment of the forearm?

A

To produce extension at the wrist and fingers

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3
Q

What are the extensor muscles innervated by?

A

The radial nerve

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4
Q

What can the muscles of the posterior forearm be divided into?

A

Two layers, deep and superficial

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5
Q

What divides the layers of muscles in the posterior forearm?

A

A layer of fascia

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6
Q

How many muscles are in the superficial layer of the posterior forearm?

A

6

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7
Q

What are the muscles of the superficial layer of the posterior forearm?

A 
Brachioradialis
 Extensor carpi radialis longus
 Extensor carpi radialis brevis
 Extensor digitorum
 Extensor digiti minimi
 Extensor carpi ulnaris
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8
Q

What muscles share a common tendinous origin at the lateral epicondyle?

A

Extensor carpi radialis longus
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris

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9
Q

Why is the brachioradialis a paradoxical muscle?

A

Because its origin and innervation are characteristic of an extensor muscle, but its actually a flexor at the elbow

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10
Q

When is the brachioradialis most visible?

A

When the forearm is half pronated, and flexing elbow against resistance

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11
Q

Where are the radial artery and nerve found in the distal forearm?

A

Sandwiched between the brachioradialis and the deep flexor muscles

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12
Q

What is the innervation of the brachioradialis?

A

Radial nerve (C5, C6, C7)

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13
Q

What is the arterial supply of the brachioradialis?

A

Radial recurrent artery

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14
Q

What is the main action of the brachioradialis?

A

Relatively weak flexion of the forearm, maximal when the forearm is in mid-pronated position

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15
Q

Where are the extensor carpi radialis muscles situated?

A

On the lateral aspect of the posterior forearm

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16
Q

What are the extensor carpi radialis muscles able to do due to their position?

A

Produce abduction as well as extension at the wrist

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17
Q

What is the innervation of the ECRL?

A

Radial nerve (C6, C7)

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18
Q

What is the arterial supply of the ECRL?

A

Radial artery

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19
Q

What is the innervation of the ECRB?

A

Deep branch of radial nerve (C7, C8)

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20
Q

What is the arterial supply of the ECRB?

A

Radial artery

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21
Q

What is the main action of the extensor carpi radialis muscles?

A

Extend and abduct the hand at the wrist joint

ECRL active during fist clenching

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22
Q

How is the function of the extensor digitorum tested?

A

The forearm is pronated, and the fingers extended against resistance

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23
Q

What is the innervation of the extensor digitorum?

A

Deep branch of radial nerve (C7, C8)

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24
Q

What is the arterial supply of the extensor digitorum?

A

Recurrent interosseous artery

Posterior interosseous artery

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25
Q

What is the action of the extensor digitorum?

A

Extends medial four digits primarily at metacarpophalangeal joints, secondarily at interphalangeal joints

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26
Q

What is true in some people regarding the extensor digiti minimi?

A

This muscle and the extensor digitorum muscle are fused together

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27
Q

Where does the extensor digiti minimi (EDM) lie?

A

Medially to the extensor digitorum

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28
Q

What is the innervation of the EDM?

A

Deep branch of radial nerve (C7, C8)

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29
Q

What is the arterial supply of the EDM?

A

Posterior interosseous artery

30
Q

What is the main action of the EDM?

A

Extends 5th digit primarily at metacarpophalangeal joint, secondarily at interphalangeal joint

31
Q

Where is the extensor carpi ulnaris (EDU) found?

A

On the medial aspect of the posterior forearm

32
Q

What is the EDU able to do due to its position?

A

Produce adduction as well as extension at the wrist

33
Q

What is the innervation of the ECU?

A

Deep branch of the radial nerve (C7, C8)

34
Q

What is the arterial supply of the ECU?

A

Ulnar artery

35
Q

What is the main action of the ECU?

A

Extends and adducts the hand at the wrist joint

Active during fist clenching

36
Q

What does lateral epicondylitis refer to?

A

Inflammation of the periosteum of the lateral epicondyle

37
Q

What is the peak age of onset of lateral epicondylitis?

A

40-50 years

38
Q

What is lateral epicondylitis caused by?

A

Repeated use of the superficial extensor muscles, which stains their common tendinous attachment of the lateral epicondyle

39
Q

How many muscles are in the deep compartment of the posterior forearm?

A

5

40
Q

What muscles are in the deep compartment of the posterior forearm?

A 
Supinator
 Abductor pollicis longus
 Extensor pollicis brevis
 Extensor pollicis longus
 Extensor indicis
41
Q

What do the deep muscles of the posterior forearm do?

A

Act on the thumb and index finger, with the exception of the supinator

42
Q

Where does the supinator lie?

A

On the floor of the cubital fossa

43
Q

What does the supinator have?

A

Two heads

44
Q

What passes between the two heads of the supinator?

A

The deep branch of the radial nerve

45
Q

What is the innervation of the supinator?

A

Deep branch of radial nerve (C7, C8)

46
Q

What is the arterial supply to the supinator?

A

Recurrent interosseous artery

47
Q

What is the main action of the supinator?

A

Supinates forearm- rotates radius to turn palm anteriorly or superiorly (if elbow are flexed)

48
Q

Where is the abductor pollicis longus?

A

Immediately distal to the supinator muscle

49
Q

What does the tendon of the abdutor pollicis longus contribute to?

A

The lateral border of the anatomical snuffbox

50
Q

What is the innervation of the APL?

A

Posterior interosseous nerve (C7, C8), a continuation of the deep branch of the radial nerve

51
Q

What is the arterial supply of the APL?

A

Posterior interosseous artery

52
Q

What is the main action of the APL?

A

Abducts the thumb and extends it at the carpometacarpal joint

53
Q

Where can the extensor pollicis brevis be found?

A

Medially and deep to the abductor pollicis longus

54
Q

What does the tendon of the EPB contribute to?

A

The lateral border of the anatomical snuffbox

55
Q

What is the innervation of the EPB?

A

Posterior interosseous nerve (C7, C8), a continuation of the deep branch of the radial nerve

56
Q

What is the arterial supply of the EPB?

A

Posterior interosseous artery

57
Q

What is the main action of the EPB?

A

Extends proximal phalanx of thumb at metacarpophalgeal joint
Extends carpometacarpal joint

58
Q

How does the extensor pollicis longus different from the EPB?

A

It has a larger muscle belly

59
Q

Where does the tendon of the EPL travel?

A

Medially to the dorsal tubercle at the wrist

60
Q

What does the tendon of the EPL act to do?

A

Uses the dorsal tubercle as a ‘pulley’ to increase the force exerted

61
Q

What does the tendon of the EPL form?

A

The medial border of the anatomical snuffbox

62
Q

What is the innervation of the EPL?

A

Posterior interosseous nerve (C7, C8), a continuation of the deep branch of the radial nerve

63
Q

What is the arterial supply of the EPL?

A

Posterior interosseous artery

64
Q

What is the main action of the EPL?

A

Extends distal phalanx of thumb at interphalangeal joints

Extends metacarpophalangeal and carpometacarpal joints

65
Q

What does the extensor indicis proprius allow?

A

The index finger to be independent of the other fingers during extension

66
Q

What is the innervation of the EIP?

A

Posterior interosseous nerve (C7, C8), a continuation of the deep branch of the radial nerve

67
Q

What is the arterial supply of the EIP?

A

Posterior interosseous artery

68
Q

What is the main action of the EIP?

A

Extends 2nd digit (enabling independent extension)

Helps extend hand at wrist

69
Q

What is wrist drop a sign of?

A

Radial nerve injury that has occurred proximal to the elbow

70
Q

What are the common characteristic sites of damage with wrist drop?

A

Axilla

Radial groove of humerus

71
Q

What causes wrist drop?

A

The radial nerve innervates all muscles in the extensor compartment of the forearm. In the event of a radial nerve lesion, these muscles areparalysed. The muscles that flex the wrist are innervated by themedian nerve, and thus are unaffected. The tone of the flexor muscles produces unopposed flexion at the wrist joint – wrist drop.

ESA 2- Musculoskeletal System (69 decks)

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