Functional Anatomy of the Forearm and Hand

Question 1

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

Answer 1

60%

Question 2

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

Answer 2

ulnar (medial) side

Question 3

What finger is the least important?

Answer 3

index finger

Question 4

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

Answer 4

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)

Question 5

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

Answer 5

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

Question 6

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

Answer 6

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

Question 7

joints of the wrist

Answer 7

radiocarpal joint

distal radioulnar joint

Question 8

radiocarpal joint

Answer 8

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

Question 9

distal radioulnar joint

Answer 9

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

Question 10

structures of the midcarpal joint

Answer 10

two rows of carpal bones, the proximal and distal

Question 11

proximal row of the midcarpal joint

Answer 11

scaphoid - “skiff”, boat

lunate - moon shaped

trquetrum - 3-sided

pisiform - pea shaped

Question 12

distal row of the midcarpal joints

Answer 12

trapezium - table

trapezoid

capitate - head

harmate - hook

Question 13

structure and function of the scaphoid bone

Answer 13

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

Question 14

carpal tunnel

Answer 14

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

Question 15

carpometacarpal joints

Answer 15

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

Question 16

metacarpophalangeal joints

Answer 16

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

Question 17

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

Answer 17

from the medial epicondyle of the humerous

Question 18

Where do the extensors of the forearm come from?

Answer 18

the lateral epicondyle

Question 19

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

Answer 19

flexor digitorum profundus

flexor pollicis longus

pronator quadratus

Question 20

What nerves innervate the flexors of the forearm?

Answer 20

median and ulnar nerves

Question 21

What nerves innervate the extensors of the forearm?

Answer 21

radial nerve

one exception is the brachioradialis muscle

Question 22

wrist extensors

Answer 22

extensor carpi radialis (longus and brevis)

extensor carpi ulnaris

Question 23

finger extensors

Answer 23

extensor digitorum (4 fingers)

extensor indicis (index), extensor

digiti minimi (small)

Question 24

thumb extensors

Answer 24

extensor pollicis longus (inserts on distal)

phalanx and brevis (proximal phalanx)

Question 25

thumb abductor

Answer 25

abductor pollicis longus (brevis is an intrinsic muscle)

Question 26

brachioradialis muscle

Answer 26

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

Question 27

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

Answer 27

ptonators - pronator teres and pronator quadratus supinators - supinator and biceps muscle

Question 28

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

Answer 28

**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

Question 29

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

Answer 29

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

Question 30

Describe the structure of the tissues surrounding the flexor tendons.

Answer 30

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

Question 31

vincula

Answer 31

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

Question 32

fibrous digital tendon sheats of the hands

Answer 32

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

Question 33

trigger finger

Answer 33

swelling of flexor tendon within a restricting fibrous sheath finter will lock into a curved, flexed orientation

Question 34

muscles of the deep flexor compartments

Answer 34

flexor digitorum profundus pronator quadratus flexor pollicis longus

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

anatomical snuff box

Answer 37

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

Question 38

Describe the extensor mechanism of the hand.

Answer 38

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

Question 39

What are the groups of muscles in the hand?

Answer 39

thenar muscles of the tumb hypothenar muscles of the small finger intrinsic muscles of the 2nd-5th fingers

Question 40

What are the thenar muscles?

Answer 40

**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

Question 41

What are the hypothenar muscles?

Answer 41

**abductor digiti minimi** **flexor digiti minimi** **opponens digiti minimi** innervated by the ulnar nerve

Question 42

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

Answer 42

dorsal and palmar interossei muscles lumbrical muscles

Question 43

What si the trolle of the three palmar interossei muscles?

Answer 43

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

Question 44

What is the role of the four dorsal interossei muscles?

Answer 44

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

Question 45

What is the role of the four lumbrical muscles?

Answer 45

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

Question 46

What does the median nerve innervate?

Answer 46

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

Question 47

What muscles is the median nerve motor to?

Answer 47

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)

Question 48

What does the recurrent branch of the median nerve supply?

Answer 48

thenar muscle vulnerable in its subcutaneous location

Question 49

What is the function of the ulnar nerve?

Answer 49

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

Question 50

What happens when the ulnar nerve is lost?

Answer 50

a variation of claw hand results M-P joints are extended and the I-P joints flex

Question 51

Where is the most common site of ulnar nerve damage?

Answer 51

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)

Question 52

What is the function of the radial nerve?

Answer 52

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

Question 53

"waiter's tip" configuration of the forearm

Answer 53

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

Question 54

midpalmar space

Answer 54

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

Question 55

thenar space

Answer 55

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

Question 56

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

Answer 56

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

Question 57

What is the structure of the ulnar artery?

Answer 57

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

Question 58

What is the structure of the radial artery?

Answer 58

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

Question 59

What is the structure of the digital arteries?

Answer 59

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

Question 60

What is the transverse carpal ligament?

Answer 60

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

Question 61

What is in the carpal tunnel?

Answer 61

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

Question 62

What are the causes of carpal tunnel syndrome?

Answer 62

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

Question 63

What are the symptoms of carpal tunnel syndrome?

Answer 63

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