Muscles of the Posterior Forearm Flashcards Preview

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Flashcards in Muscles of the Posterior Forearm Deck (93):
1

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

The extensor muscles

2

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

To produce extension at the wrist and fingers

3

What are the extensor muscles innervated by?

The radial nerve

4

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

Two layers, deep and superficial

5

What divides the layers of muscles in the posterior forearm?

A layer of fascia

6

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

6

7

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

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

8

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

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

9

Why is the brachioradialis a paradoxical muscle?

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

10

When is the brachioradialis most visible?

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

11

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

Sandwiched between the brachioradialis and the deep flexor muscles

12

What is the proximal attachment of the brachioradialis?

Proximal two thirds of the supra-epicondylar ridge of humerus

13

What is the distal attachment of the brachioradialis?

Lateral surface of distal end of radius, proximal to styloid process

14

What is the innervation of the brachioradialis?

Radial nerve (C5, C6, C7)

15

What is the arterial supply of the brachioradialis?

Radial recurrent artery

16

What is the main action of the brachioradialis?

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

17

Where are the extensor carpi radialis muscles situated?

On the lateral aspect of the posterior forearm

18

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

Produce abduction as well as extension at the wrist

19

What is the proximal attachment of the extensor carpi radialis longus (ECRL)?

Lateral supra-epicondylar ridge of humerus

20

What is the distal attachment of the ECRL?

Dorsal aspect of base of 2nd metacarpal?

21

What is the innervation of the ECRL?

Radial nerve (C6, C7)

22

What is the arterial supply of the ECRL?

Radial artery

23

What is the proximal attachment of the extensor carpi radialis brevis (ECRB)?

Lateral epicondyle of humerus (common extensor origin)

24

What is the distal attachment of the ECRB?

Dorsal aspect of base of 3rd metacarpal

25

What is the innervation of the ECRB?

Deep branch of radial nerve (C7, C8)

26

What is the arterial supply of the ECRB?

Radial artery

27

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

Extend and abduct the hand at the wrist joint
ECRL active during fist clenching

28

How is the function of the extensor digitorum tested?

The forearm is pronated, and the fingers extended against resistance

29

What is the proximal attachment of the extensor digitorum?

Lateral epicondyle of humerus (common extensor origin)

30

What is the distal attachment of the extensor digitorum?

Extensor expansions of medial four digits

31

What is the innervation of the extensor digitorum?

Deep branch of radial nerve (C7, C8)

32

What is the arterial supply of the extensor digitorum?

Recurrent interosseous artery 
Posterior interosseous artery

33

What is the action of the extensor digitorum?

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

34

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

This muscle and the extensor digitorum muscle are fused together

35

Where does the extensor digiti minimi (EDM) lie?

Medially to the extensor digitorum

36

What is the proximal attachment of the EDM?

Lateral epicondyle of humerus (common extensor origin)

37

What is the distal attachment of the EDM?

Extensor expansion of 5th digit

38

What is the innervation of the EDM?

Deep branch of radial nerve (C7, C8)

39

What is the arterial supply of the EDM?

Posterior interosseous artery

40

What is the main action of the EDM?

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

41

Where is the extensor carpi ulnaris (EDU) found?

On the medial aspect of the posterior forearm

42

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

Produce adduction as well as extension at the wrist

43

What is the proximal attachment of the ECU?

Lateral epicondyle of the humerus 
Posterior border of ulna via a shared aponeurosis

44

What is the distal attachment of the ECU?

Dorsal aspect of base of 5th metacarpal

45

What is the innervation of the ECU?

Deep branch of the radial nerve (C7, C8)

46

What is the arterial supply of the ECU?

Ulnar artery

47

What is the main action of the ECU?

Extends and adducts the hand at the wrist joint 
Active during fist clenching

48

What does lateral epicondylitis refer to?

Inflammation of the periosteum of the lateral epicondyle

49

What is the peak age of onset of lateral epicondylitis?

40-50 years

50

What is lateral epicondylitis caused by?

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

51

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

5

52

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

Supinator 
Abductor pollicis longus 
Extensor pollicis brevis
Extensor pollicis longus 
Extensor indicis

53

What do the deep muscles of the posterior forearm do?

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

54

Where does the supinator lie?

On the floor of the cubital fossa

55

What does the supinator have?

Two heads

56

What passes between the two heads of the supinator?

The deep branch of the radial nerve

57

What is proximal attachment of the supinator?

Lateral epicondyle of the humerus 
Radial collateral and anular ligaments
Supinator fossa
Crest of ulna

58

What is the distal attachment of the supinator?

Lateral, posterior and anterior surfaces of the proximal third of the radius

59

What is the innervation of the supinator?

Deep branch of radial nerve (C7, C8)

60

What is the arterial supply to the supinator?

Recurrent interosseous artery

61

What is the main action of the supinator?

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

62

Where is the abductor pollicis longus?

Immediately distal to the supinator muscle

63

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

The lateral border of the anatomical snuffbox

64

What is the proximal attachment of the APL?

Posterior surface of proximal haves of ulna, radius, and interosseous membrane

65

What is the distal attachment of the APL?

Base of 1st metacarpal

66

What is the innervation of the APL?

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

67

What is the arterial supply of the APL?

Posterior interosseous artery

68

What is the main action of the APL?

Abducts the thumb and extends it at the carpometacarpal joint

69

Where can the extensor pollicis brevis be found?

Medially and deep to the abductor pollicis longus

70

What does the tendon of the EPB contribute to?

The lateral border of the anatomical snuffbox

71

What is the proximal attachment of the EPB?

Posterior surface of the distal third of the radius and interosseous membrane

72

What is the distal attachment of the EPB?

Dorsal aspect of base of proximal phalanx of thumb

73

What is the innervation of the EPB?

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

74

What is the arterial supply of the EPB?

Posterior interosseous artery

75

What is the main action of the EPB?

Extends proximal phalanx of thumb at metacarpophalgeal joint 
Extends carpometacarpal joint

76

How does the extensor pollicis longus different from the EPB?

It has a larger muscle belly

77

Where does the tendon of the EPL travel?

Medially to the dorsal tubercle at the wrist

78

What does the tendon of the EPL act to do?

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

79

What does the tendon of the EPL form?

The medial border of the anatomical snuffbox

80

What is the proximal attachment of the EPL?

Posterior surface of middle third of ulna and interosseous membrane

81

What is the distal attachment of the EPL?

Dorsal aspect of the base of distal phalanx

82

What is the innervation of the EPL?

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

83

What is the arterial supply of the EPL?

Posterior interosseous artery

84

What is the main action of the EPL?

Extends distal phalanx of thumb at interphalangeal joints
Extends metacarpophalangeal and carpometacarpal joints

85

What does the extensor indicis proprius allow?

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

86

What is the proximal attachment of EIP?

Posterior surface of distal third of ulna and interosseous membrane

87

What is the distal attachment of the EIP?

Extensor expansion of 2nd digit

88

What is the innervation of the EIP?

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

89

What is the arterial supply of the EIP?

Posterior interosseous artery

90

What is the main action of the EIP?

Extends 2nd digit (enabling independent extension)
Helps extend hand at wrist

91

What is wrist drop a sign of?

Radial nerve injury that has occurred proximal to the elbow

92

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

Axilla 
Radial groove of humerus

93

What causes wrist drop?

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