Hand B&B

Question 1

what is the anatomical terminology for the palm vs back of hand?

Answer 1

palm of hand = volar
back of hand = dorsal

Question 2

which nerves innervate the hand and what are their respective distributions?

Answer 2

1. Ulnar nerve - innervates structures toward the ulnar bone (uLnar innervates Little finger)
2. Median nerve - innervates structures towards the radius (Median innervates thuMb)

Question 3

what are the four intrinsic muscle groups of the hand?

Answer 3

1. thenar – thumb muscle
2. hypothenar - little finger
3. interosseous - between fingers for abduction/adduction
4. lumbrical - flex/extend the 4 fingers

Question 4

what are the 3 thenar muscles and how are they innervated?

Answer 4

1. abductor pollicis brevis
2. flexor pollicis brevis
3. opponens pollicis
   [so basically you can abduct, flex, and oppose your thumb]

innervated by the median nerve and may atrophy following lesion

Question 5

what are the 3 hypothenar muscles and how are they innervated?

Answer 5

(muscles of little finger, form hypothenar eminence)
1. opponens digiti minimi
2. flexor digiti minimi brevis
3. abductor digiti minimi

innervated by ulnar nerve and may atrophy following lesion

Question 6

what muscle movement is carried out by interosseous muscles on the dorsal and palmar side of the hand, respectively?

Answer 6

dorsal side = abduction
palmar side = adduction

all innervated by ulnar nerve

Question 7

from where do the lumbrical hand muscles originate?

Answer 7

originate at the tendons of the flexor digitorum profundus (forearm muscle that flexes fingers)

lumbrical muscles flex metacarpophalangeal joints + extend interphalangeal joints (make L shape with hand)

Question 8

describe the innervation of the lumbrical hand muscles

Answer 8

medial 2 lumbricals (near Little finger) - uLnar nerve

lateral 2 lumbricals (near thuMb) - Median nerve

lumbrical muscles flex metacarpophalangeal joints + extend interphalangeal joints (make L shape with hand)

Question 9

what occurs from loss of lumbrical innervation of the hand? explain why

Answer 9

loss of lumbricals —> claw fingers (metacarpophalangeal joints extended, interphalangeal joints flexed)

lumbrical muscles flex metacarpophalangeal joints + extend interphalangeal joints (make L shape with hand)

[loss of uLnar nerve = median/Little finger side clawed, loss of Median nerve = lateral/ Thumb side clawed]

Question 10

which muscle of the underside of the forearm is responsible for flexing the digits to make a fist?

Answer 10

flexor digitorum profundus

innervate by Median (thuMb side) and uLnar (Little finger side) nerves

Question 11

which nerves innervate the MCP, PIP, and DIP joints to allow extension of the fingers, respectively?

Answer 11

MCP (metacarpophalangeal) - radial nerve, via extensor digitorum of the forearm

PIP/DIP (proximal/distal interphalangeal) - uLnar nerve for Little finger side, Median nerve for thuMb side

Question 12

the major extensors of the wrist are all innervated by which nerve?

Answer 12

radial nerve - lesion causes wrist drop

1. extensor carpi radialis longus
2. extensor carpi radialis brevis
3. extensor carpi ulnaris

Question 13

Upon trying to make a fist, a patient’s hand takes the shape of a “Pope’s blessing,” with only their ring and pink finger flexed. Which nerve has been lesioned?

Answer 13

Median nerve - innervates the flexors of the thuMb side hand

Question 14

a supracondylar fracture of the humerus may result in [median/ulnar] deviation of the wrist

Answer 14

supracondylar fracture = just above the elbow

may cause median nerve lesion —> loss of most flexors in forearm —> ulnar deviation
(via flexor carpi ulnaris)

Question 15

what is the function of the recurrent branch of the median nerve?

Answer 15

motor innervation to thenar muscles of the hand (NOT sensory)

superficial nerve near flexor retinaculum (forms carpal tunnel), may be injured in superficial laceration —> immobilized thumb, but sensation intact

Question 16

an elbow fracture at the medial epicondyle may result in [median/ulnar] deviation of the wrist

Answer 16

ulnar nerve runs right along medial epicondyle

fracture causes ulnar nerve lesion (loss of flexor carpi ulnaris) —> radial deviation of wrist with flexion

Question 17

how can functionality of the flexor digitorum profundus be differentiated from the flexor digitorum superficialis?

Answer 17

FDS travels only as far as PIP, but FDP travels all the way to DIP

so if patient cannot flex distal interphalangeal joint, the damage is to the flexor digitorum profundus