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MSK/Derm > Functional Anatomy of the Forearm and Hand > Flashcards

Functional Anatomy of the Forearm and Hand Flashcards

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Dermatology Board Prep flashcards
1
Q

How much of the function of the hand does the thumb give?

A

60%

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2
Q

What side of the hand is the most important for power grip?

A

ulnar (medial) side

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3
Q

What finger is the least important?

A

index finger

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4
Q

What are the major divisions of bones in the forarm and hands?

A

radius and ulna of the forearm

8 carpal bones in the hand separated into proximal and distal rows

5 metacarpal bones in the hands

fingers are composed of proximal, middle, and distal phalanges (thumb has only 2 phalanges, the proximal and distal)

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5
Q

What structures form the hinge joint for flexion and extension in the elbow?

A

the trochlear notch of the ulna articulates with the trochlea of the humerus

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6
Q

What skeletal structures are responsible for the pronation and supination movements of the forearm and hand?

A

the concave head of the radius pivots on the capitulum of the humerus

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7
Q

joints of the wrist

A

radiocarpal joint

distal radioulnar joint

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8
Q

radiocarpal joint

A

the radius articulates with the scaphoid and lunate carpal bones

in compression most of the weight is transferred between the scaphoid bone and radius

fractures of these bones are the most common fractures of the forearm/hand

considered to be a bi-axial joint: flexion/extension and radial deviation (abduction)/ulnar deviation (adduction) occur

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9
Q

distal radioulnar joint

A

radius can rotate around the head of the ulna to allow for pronation/supination

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10
Q

structures of the midcarpal joint

A

two rows of carpal bones, the proximal and distal

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11
Q

proximal row of the midcarpal joint

A

scaphoid - “skiff”, boat

lunate - moon shaped

trquetrum - 3-sided

pisiform - pea shaped

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12
Q

distal row of the midcarpal joints

A

trapezium - table

trapezoid

capitate - head

harmate - hook

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13
Q

structure and function of the scaphoid bone

A

extends into both the proximal and distal rows of the midcarpal joint

while there is little movement between carpal bones, the scaphoid acts as a strut to stabilize movements between the proximal and distal row

fracture of the scaphoid bones causes the scaphoid to loose its height and may lead to collapse of the wrist

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14
Q

carpal tunnel

A

an osseo-ligamentous tunnel

carpal bones form the base of the canal and hook of the hamate and tubercle of the trapezium serve as the sidewalls

the transverse carpal ligament forms the roof and spans the hook to the tubercle

the long finger flexor tendons and median nerve pass through the tunnel

this is different from the flexor retinaculum which helps confine the flexors in the distal forearm to prevent bowstringing

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15
Q

carpometacarpal joints

A

little movement occurs here, except for the carpometacarpal joint of the thumb

this is a saddle joint articulation of the trapezium with the first metacarapl and allows for three planes of movement

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16
Q

metacarpophalangeal joints

A

bi-axial joints with flexion/extension and abduction/adduction movements (but no rotation)

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17
Q

Where do flexor muscles of the forearm (and the pronator teres) originate from?

A

from the medial epicondyle of the humerous

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18
Q

Where do the extensors of the forearm come from?

A

the lateral epicondyle

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19
Q

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

A

flexor digitorum profundus

flexor pollicis longus

pronator quadratus

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20
Q

What nerves innervate the flexors of the forearm?

A

median and ulnar nerves

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21
Q

What nerves innervate the extensors of the forearm?

A

radial nerve

one exception is the brachioradialis muscle

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22
Q

wrist extensors

A

extensor carpi radialis (longus and brevis)

extensor carpi ulnaris

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23
Q

finger extensors

A

extensor digitorum (4 fingers)

extensor indicis (index), extensor

digiti minimi (small)

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24
Q

thumb extensors

A

extensor pollicis longus (inserts on distal)

phalanx and brevis (proximal phalanx)

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25
Q

thumb abductor

A

abductor pollicis longus (brevis is an intrinsic muscle)

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26
Q

brachioradialis muscle

A

while the brachioradialis is an extensor compartment muscle innervated by a posterior division nerve (radial), it flexes the elbow joint because it is anterior to the traverse axis of rotation of the elbow

it is also the only long muscle of the compartment that does not cross the wrist joint

it attaches to the styloid process of the radius

27
Q

What are the muscles that support pronation and supination in the forearm

A

ptonators - pronator teres and pronator quadratus

supinators - supinator and biceps muscle

28
Q

What are the flexor tendons of fingers 2-5, and what are their structures like?

A

flexor digitorum profundus - deep flexor compartment of the forearm sends a tendon to the distal phalange of the digits to flex the wrist, MP, and both IP joints

flexor digitorum superficialis - four tendons that divides around the flexor digitorum profundus tendon to insert in the middle phalange, it cannot flex the distal IP joint

29
Q

What are the flexors of the wrist, and where do they insert?

A

flexor carpi radialis and flexor capri ulnaris

insert on the base of the 2nd and 5th metacarpals respectively

since they not only cross the wrist, they do not aid in flexion of the MP or IP joints

30
Q

Describe the structure of the tissues surrounding the flexor tendons.

A

enveloped by synovial tendon sheaths with visceral and parietal layers

contains a connecting mesotendon that has the same arrangement and function as peritoneum in the mesenteries in the abdomen

31
Q

vincula

A

short mesotendons (unlike the long mesenteries) that serve as routes of blood vessels to the tendons (like the mesenteries)

32
Q

fibrous digital tendon sheats of the hands

A

dense connective tissue ligaments that hold the flexor tendons to the phalanges to keep the tendons from “bowstringing” when the fingers flex

they act as pulleys on the bones for tendon movements

33
Q

trigger finger

A

swelling of flexor tendon within a restricting fibrous sheath

finter will lock into a curved, flexed orientation

34
Q

muscles of the deep flexor compartments

A

flexor digitorum profundus

pronator quadratus

flexor pollicis longus

35
Q

What is the structure and function of the vestigial palmaris longus?

A

muscle of the flexor compartment that terminates as the dense connective tissue expansion of the palmar aponeurosis

the aponeurosis attaches to the base of the proximal phalanges and provides a strong, deep fascial support in the palm of the hand over the long flexor tendons

36
Q

What are the differences in the extensor compartment compared with the flexor compartment of the hand?

A

there are two extensor carpi radialis muscles (longus and brevis), in addition to an extensor carpi ulnaris

only one extensor digitorum, but there are separate muscles to the index finger (extensor indicis) and little finger (extensor digiti)

three long muscles to the thumb (extensor pollicis longus and brevis and abductor pollicis longus)

extension is not as strong an action as flexion, so overuse of the extensors or the brachioradialis can result in tears at the origin of the extensor compartment or swelling (tennis elbow)

the extensors of the 2nd-5th fingers insert into the extensor mechanism (“hood”) at the level of the proximal phalanx

37
Q

anatomical snuff box

A

the recess between the two extensors when the tumb is extended

in the floow of the snuff box is the radial artery, the styloid process of the radius, and the trapezium and scaphoid bones

38
Q

Describe the extensor mechanism of the hand.

A

receives insertions from the extensor tendons and the intrinsic muscles of the hand

the extensors extend the MP and IP joints, while the intrinsics flex the MP and extend the IP joints

39
Q

What are the groups of muscles in the hand?

A

thenar muscles of the tumb

hypothenar muscles of the small finger

intrinsic muscles of the 2nd-5th fingers

40
Q

What are the thenar muscles?

A

abductor pollicis brevis - the longus is in the extensor compartment

flexor pollicis brevis - the longus is in the flexor compartment

opponens pollicis

these muscles are supplied by the median nerve

41
Q

What are the hypothenar muscles?

A

abductor digiti minimi

flexor digiti minimi

opponens digiti minimi

innervated by the ulnar nerve

42
Q

What are the three groups of intrinsic muscles in the hand?

A

dorsal and palmar interossei muscles

lumbrical muscles

43
Q

What si the trolle of the three palmar interossei muscles?

A

aduct digits 2, 4, and 5

they attach from metacarpals to proximal phalanges and extensor tendon expansions (hoods) on the appropriate sides of these fingers for adduction

44
Q

What is the role of the four dorsal interossei muscles?

A

abduct digits 2 and 4 and move digit 3 in both directions

the thenar and hypothenar compartments have abductors for the thumb and little finger, respectively

originate between adjacent metacarpals and insert int othe abducting sides of the proximal phalanges of these digits

like palmar interossei and lumbricals, they insert on bot the proximal phalanges and the extensor tendon hoods

45
Q

What is the role of the four lumbrical muscles?

A

abductions of fingers 2 and 3 and adduction of 4 and 5

originate from tendons of flexor digitorum profundus in the palm of the hand and insert into the lateral (radial) side of the proximal phalanges fo digits 2-5 laterally (radially) deviate those fingers

46
Q

What does the median nerve innervate?

A

anterior division nerve of the brachial plexus

supplies the flexor compartment of the forearm, thenar compartment of the hand and lumbricals of the 2nd (index) and 3rd (long) digits

passes with the long flexor tendons through the carpal tunnel as it courses from forearm to hands

47
Q

What muscles is the median nerve motor to?

A

flexor compartment of the forearm except flexor carpi ulnaris and the ulnar two digits of flexor digitorum profundus

the muscles of this compartment flex the wrist joints and joints of the fingers

they also pronate the forearm and abduct the wrist (adduction or ulnar deviation is ulnar nerve)

48
Q

What does the recurrent branch of the median nerve supply?

A

thenar muscle

vulnerable in its subcutaneous location

49
Q

What is the function of the ulnar nerve?

A

anterior deivision nerve

supplies most of the other intrinsic hand muscles - palmar and dorsal interosseus muscles, hypothenar compartment, medial two lumbrical muscles (4th and 5th digit) and adductor pollicis

with the ulnar artery, it passes superficial to the flexor retinaculum and carpal tunnel

50
Q

What happens when the ulnar nerve is lost?

A

a variation of claw hand results

M-P joints are extended and the I-P joints flex

51
Q

Where is the most common site of ulnar nerve damage?

A

where it passes behind the medial epicondyle of the humerus (the “funny bone”)

the nerve can also be compressed at the area (Cubital Tunnel Syndrome)

52
Q

What is the function of the radial nerve?

A

posterior division nerve whose deep branch is motor to the extensor compartment muscles

superficial branch is cutatneous to the back fo th hand on the radial side

since the radial nerve is the only extensor compartment (posterior division) nerve distal to the shoulder, loss of the radial nerve will result in flexed joints

53
Q

“waiter’s tip” configuration of the forearm

A

caused by damage in the spinal groove of the humerus

wrist drop (flexed wrist) with a pronated forearm (loss of supinator)

the triceps still has some function

damage higher up (loss of triceps) results in “chicken wing” where the elbow is in a flexed position as well

54
Q

midpalmar space

A

located between the long flexor tendons and the interosseus muscles attaching to the metacarpal bones

continuous with the flexor forearm compartment through the carpal tunnel

55
Q

thenar space

A

between the thenar compartment and adductor pollicis

the two spaces are separated from each other by a dense septum extending from the palmar aponeurosis to the third metacarpal bone

56
Q

What is the structure of the common interosseus artery? What muscles does it supply?

A

supplies the deep muscles of the flexor and extensor compartments

it is a branch of hte ulnar artery and quickly divides into anterior and posterior interosseus arteries that pass in fron tof and behnd the interosseus membrane interconnecting the radius and ulna

57
Q

What is the structure of the ulnar artery?

A

the ulnar artery branches from the brachial artery and continues in the palm as the superficial palmar arch that terminates by anastomosis with the radial artery at the wrist just proximal to the thenar compartment

58
Q

What is the structure of the radial artery?

A

branches off from the brachial artery and continues in the the palm as the deep palmar arch that connects with the deep branch of the ulnar artery that passes into the hpothenar compartment

59
Q

What is the structure of the digital arteries?

A

arteries that run on each side of the digits with corresponding digital nerves from the median and ulnar nerves

both the ulnar and radial artery contribute to the digital arteries

60
Q

What is the transverse carpal ligament?

A

ligament that closes off the anterior groove on the carpal bones

attaches to the hook of the hamate bone and tubercle of the trapezium

more proximally it attaches to the pisiform bone and tubercle of the scaphoid bone

61
Q

What is in the carpal tunnel?

A

the tendons of flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus

the median nerve also passes through the carpal tunnel

the ulnar artery and nerve and the other flexor compartment tendons crossing the wrist joint are anterior and medial to the transverse carpal ligament

62
Q

What are the causes of carpal tunnel syndrome?

A

median nerve compression in the carpal tunnel from swelling of the common synovial tendon sheath enveloping the eight flexor digitorum tendons

the swelling can result from chronic overuse of the fingers

63
Q

What are the symptoms of carpal tunnel syndrome?

A

loss of the median nerve cutaneous sensation int he hand

motor innervation of the tumb and lateral two lumbrical muscles is lost or weakened

the thenar compartment will atrophy, and thumb function will be greatly diminished

median nerve innervation of the flexor forearm compartment is unaffected, movements at the wrist are normal

MSK/Derm (54 decks)

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