functional anatomy of the hand Flashcards
proximal row of carpal bones
scaphoid, lunate, triquetrium, pisiform
distal row of carpal bones
trapezium, trapezoid, capitate, hamate
radial nerve supply of the hand
cutaneous innervation from the region along the dorsal of the hand and thumb. component of the C6 dermatome
median nerve supply of the hand
sensory innervation from the palmar surface of the first 3.5 digits. Motor innervation to thenar muscles and first 2 lumbricals
ulnar nerve supply of the hand
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
blood supply to the hand and digits
radial and ulnar arteries
carpometacarpal joints
the base of each metacarpal articulates with the distal row of carpal bones connecting the wrist to the hand
metacarpophalangeal joints
the distal portion of the metacarpal bones articulating with the proximal phalanx of of each digit
thenar eminence
fleshy, muscular area on the lateral side of the thumb formed by the thinner muscles
hypothenar eminence
fleshly area on the medial side of the 5th digit
proximal crease of the wrist
indicates the location of the articulation between the distal radius and the proximal row of the carpal bones
distal crease of the wrist
site of the articulations between the distal row of carpals and the base of the metacarpals
proximal digital crease
location of the metacarpophalangeal joints on the fingers
proximal interphalangeal crease
location of the proximal interphalangeal joint (middle knuckle)
distal interphalangeal joint
location of the distal interphalangeal joint on each finger (distal knuckle)
common synovial sheath
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.
digital synovial sheath
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
tendon sheaths
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
extrinsic extensor muscles of the fingers
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
- extensor digitorum
- extensor indicis
- extensor digiti minimi
extrinsic muscles of the thumb
- extensor pollicis longus
- extensor pollicis brevis
- adbuctor pollicis longus
posterior interosseous branch of the radial nerve
intrinsic thenar muscles
- flexor pollicis brevis
- abductor pollicis brevis
- opponens pollicis
- adductor pollicis (ulnar nerve)
recurrent (thenar) branch of the median nerve
thumb opposition steps (3)
- abductor pollocis brevis abducts MP joint & unlocks it
- flexor pollicis brevis brings the thumb across the palm by flexing the MP joint
- opponens pollicis rotates 1st metacarpal on the trapezium, enabled the pad of the thumb to touch the the pad of the other fingers
intrinsic hypothenar muscles (3)
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
- abductor digiti minimi
- flexor digiti minimi
- opponens digiti minimi
deep branch of the ulnar nerve
lumbricals
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
interossei
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
dorsal digital expansion functions
- 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
components of the dorsal digital expansion
- 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 - bands
- central bands extends the base of the middle phalanx of each finger
- 2 lateral bands extend to distal phalanx of each finger
role of interossei and lumbricals in dorsal digital expansion
- interossei joins the hood close to MP joint and acts as the primary flexors of them
- 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
ulnar artery
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
radial artery
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
movement of the MP joints of fingers
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)
movement of IP joints of fingers
flexion: curling fingers, (flexor digitorum superficialis on procimal IP and profundus on distal IP)
movements of the MP joints of the thumb
extensor pollicis brevis: extends
flexor pollicis brevis: flexes
adductor pollicis: adducts
abductor pollicis brevis: abducts
movements of the IP joints of the thumb
extensor pollicis longus
flexor pollicis longus
movement of the 1st carpometacarpal joint
abductor pollicis longus: abducts
adductor pollicis: adducts along w/ MP joint of thumb
opponens pollicis: rotates
opposition of the thumb
allows humans to grasp things, 4 steps
- abductor pollicis brevis abducts MP joint unlocking it
- flexor pollicis brevis flexes MP joint
- opponens pollicis rotates 1st MC bone of trapezium
- complete opposition also requires flexion of IP joint by flexor pollicis longs and some flexion at 1st CMC joint by adductor pollicis
