functional anatomy of the hand

Question 1

proximal row of carpal bones

Answer 1

scaphoid, lunate, triquetrium, pisiform

Question 2

distal row of carpal bones

Answer 2

trapezium, trapezoid, capitate, hamate

Question 3

radial nerve supply of the hand

Answer 3

cutaneous innervation from the region along the dorsal of the hand and thumb. component of the C6 dermatome

Question 4

median nerve supply of the hand

Answer 4

sensory innervation from the palmar surface of the first 3.5 digits. Motor innervation to thenar muscles and first 2 lumbricals

Question 5

ulnar nerve supply of the hand

Answer 5

divides into superficial and deep branches near the wrist. Superficial: cutaneous innervation from the medial (ulnar) 1.5 digits and the ulnar potion of the hand. C8 dermatome
deep: hypothenar mucles, all interossei, adductor policies and medial 2 lumbricals

Question 6

blood supply to the hand and digits

Answer 6

radial and ulnar arteries

Question 7

carpometacarpal joints

Answer 7

the base of each metacarpal articulates with the distal row of carpal bones connecting the wrist to the hand

Question 8

metacarpophalangeal joints

Answer 8

the distal portion of the metacarpal bones articulating with the proximal phalanx of of each digit

Question 9

thenar eminence

Answer 9

fleshy, muscular area on the lateral side of the thumb formed by the thinner muscles

Question 10

hypothenar eminence

Answer 10

fleshly area on the medial side of the 5th digit

Question 11

proximal crease of the wrist

Answer 11

indicates the location of the articulation between the distal radius and the proximal row of the carpal bones

Question 12

distal crease of the wrist

Answer 12

site of the articulations between the distal row of carpals and the base of the metacarpals

Question 13

proximal digital crease

Answer 13

location of the metacarpophalangeal joints on the fingers

Question 14

proximal interphalangeal crease

Answer 14

location of the proximal interphalangeal joint (middle knuckle)

Question 15

distal interphalangeal joint

Answer 15

location of the distal interphalangeal joint on each finger (distal knuckle)

Question 16

common synovial sheath

Answer 16

surround the tendons of the flexor digitorum superficialis and profundus. start just proximal to the carpal tunnel and conducts the tendons from there through the middle of the palm.

Question 17

digital synovial sheath

Answer 17

surrounds the combined tendons to each finger and continue to the base of the distal phalanx.

provides lubrication to help the tendons move without resulting in pain and inflammation

the digital synovial sheath in the 5th digit is continuous with the common synovial sheath of all 4 fingers in the palm forming the ulnar bursar

Question 18

tendon sheaths

Answer 18

kept applied to the bones of the fingers by fibrous digital sheaths. made up of:
-dense annular and weaker cruciate ligaments extending from the synovial sheaths to the base of the distal phalanx of each finger that are attached at the IP and MP joints to fibrocartilage palmar plates

the tendon of the flexor policies longs is surrounded by its own digital sheath, sometimes referred to as the radial bursa

Question 19

extrinsic extensor muscles of the fingers

Answer 19

arise in the extensor region of the forearm, pass though the extensor retinaculum on the dorsum of the wrist.

exert their primary action on the MP joints of the fingers

1. extensor digitorum
2. extensor indicis
3. extensor digiti minimi

Question 20

extrinsic muscles of the thumb

Answer 20

1. extensor pollicis longus
2. extensor pollicis brevis
3. adbuctor pollicis longus

posterior interosseous branch of the radial nerve

Question 21

intrinsic thenar muscles

Answer 21

1. flexor pollicis brevis
2. abductor pollicis brevis
3. opponens pollicis
4. adductor pollicis (ulnar nerve)

recurrent (thenar) branch of the median nerve

Question 22

thumb opposition steps (3)

Answer 22

1. abductor pollocis brevis abducts MP joint & unlocks it
2. flexor pollicis brevis brings the thumb across the palm by flexing the MP joint
3. opponens pollicis rotates 1st metacarpal on the trapezium, enabled the pad of the thumb to touch the the pad of the other fingers

Question 23

intrinsic hypothenar muscles (3)

Answer 23

located on the ulnar side of the 5th metacarpal. proximal attachments of all 3 are on the medial side of the flexor retinaculum, the pisiform bone and the hamate bone

1. abductor digiti minimi
2. flexor digiti minimi
3. opponens digiti minimi

deep branch of the ulnar nerve

Question 24

lumbricals

Answer 24

worm-like muscles that arise from the flexor digitorum profundus. each muscle crosses anterior to the MP joint to insert onto the dorsal digital expansion

flex the MP joints while extending the IP joints

median (1&2) and ulnar (3&4) nerves

Question 25

interossei

Answer 25

arise from the metacarpal bones deep in the palm. 4 dorsal, 3 palmer. flexors of the MP joints palmer: arise from the palmer surface of MC bones 2,4,5 and inert into dorsal digital expansion and proximal phalanges of 2,4,5. adduct MP joints and flex dorsal: arise from adjacent surfaces of MC bones and insert into dorsal digital expansion and proximal phalanges of digits 2,3,4. abduct MP joints of digits 2,3,4. deep branch of the ulnar nerve

Question 26

dorsal digital expansion functions

Answer 26

- enables the extrinsic extensor tendons to strongly extend the MP joints of the fingers - extend the IP joints of the fingers only when MP joints are flexed by finger flexors

Question 27

components of the dorsal digital expansion

Answer 27

1. extensor hood: - covers MP joint of each finger - formed by tissue connecting the tendons of the extensor digitorum, interossei, and the lumbricals of each finger - ext. indices tendon joins the hood of the 2nd digit - ext digiti minimi joins the hood of the pinky 2. bands - central bands extends the base of the middle phalanx of each finger - 2 lateral bands extend to distal phalanx of each finger

Question 28

role of interossei and lumbricals in dorsal digital expansion

Answer 28

1. interossei joins the hood close to MP joint and acts as the primary flexors of them 2. lumbricals join the expansion distal to interpose and affect the central and lateral bands. Primary extenders of the IP joints when MP joints are flexed

Question 29

ulnar artery

Answer 29

large superficial branch, joins the smaller branch of the radial artery to form the superficial palmar arch which supplies skin and superficial structures of the hand

Question 30

radial artery

Answer 30

deep branch: larger than superficial, crosses within the anatomical snuff box before passing through the heads of the dorsal interosseous muscles, then crosses over the palmar surface of the MC bones to join the deep branch of the ulnar artery. superficial branch: courses along the palmar surface of the MC bones in company of the deep branch of the ulnar nerve

Question 31

movement of the MP joints of fingers

Answer 31

extension: fingers brought away from palmar surface of hand (extensor digitorum, indices, digit minimi) flexion: fingers toward palmar surface. (interossei, lumbricals can flex only when they simultaneously extend the IP joints) abduction: moving 2 and 4 and 5 away from 3 (midline), or moving 3 medially or laterally (dorsal interossei) adduction: moving toward the midline. (palmar interossei)

Question 32

movement of IP joints of fingers

Answer 32

flexion: curling fingers, (flexor digitorum superficialis on procimal IP and profundus on distal IP)

Question 33

movements of the MP joints of the thumb

Answer 33

extensor pollicis brevis: extends flexor pollicis brevis: flexes adductor pollicis: adducts abductor pollicis brevis: abducts

Question 34

movements of the IP joints of the thumb

Answer 34

extensor pollicis longus | flexor pollicis longus

Question 35

movement of the 1st carpometacarpal joint

Answer 35

abductor pollicis longus: abducts adductor pollicis: adducts along w/ MP joint of thumb opponens pollicis: rotates

Question 36

opposition of the thumb

Answer 36

allows humans to grasp things, 4 steps 1. abductor pollicis brevis abducts MP joint unlocking it 2. flexor pollicis brevis flexes MP joint 3. opponens pollicis rotates 1st MC bone of trapezium 4. complete opposition also requires flexion of IP joint by flexor pollicis longs and some flexion at 1st CMC joint by adductor pollicis