Documents
Resources
Learning Center
Upload
Plans & pricing Sign in
Sign Out

Kines 171 Hands - STRUCTURE OF THE HAND

VIEWS: 25 PAGES: 14

									 STRUCTURE OF THE HAND
• Carpals (8); scaphoid, lunate, triquetral,
  pisiform, trapezium, trapezoid, capitate, and
  hamate
• Metacarpals (5); proximal base, medial
  body, and distal head
• Phalanges (14); proximal, medial, & distal
  (the thumb has only proximal and distal)
     JOINTS OF THE WRIST
• The wrist joints are composed of the
  radiocarpal joints and the intercarpal joints
  – radiocarpal joint formed by the distal end of the
    radius, an articular disk, and (3) of the (4)
    carpal bones in the proximal row (scaphoid,
    lunate & triquetral)
  – intercarpal joints are divided into (3) groups:
    the joints between the proximal row bones; the
    joints between the distal row bones; and the
    midcarpal joint, the joint between the (2) rows
     JOINTS OF THE HAND
• There are (12) hinge joints and (5) universal
  joints in the hand allowing for (22) degrees
  of freedom; note the thumb’s
  carpometacarpal joint is also called a saddle
  joint permitting extensive and unique mvts.
  – Hinge joints (within the phalanges) 1 dof
  – Universal joints (MP) 2 dof
   MUSCLES OF THE WRIST
        AND HAND
• Six principle muscles act on the wrist,
  although the extrinsic muscles of the hand
  can act as agonists: flexor carpi radialis,
  flexor carpi ulnaris, flexor digitorum
  superficialis, extensor carpi radialis longus,
  extensor carpi radialis brevis, and extensor
  carpi ulnaris
   MUSCLES OF THE WRIST
        AND HAND
• Intrinsic muscles of the hand are sub-
  divided into (3) groups: those of the thumb
  (thenar eminence) on the radial side, those
  of the little finger (hypothenar eminence)on
  the ulnar side, and those in the middle of the
  hand and between the metacarpals.
• (11) small intrinsic muscles are involved
  with mvt of the fingers (4) lumbricals, (4)
  dorsal interossei, & (3) palmar interossei
   MUSCLES OF THE WRIST
        AND HAND
• (3) muscles act only on the little finger: abductor
  digiti minimi, flexor digiti minimi brevis, &
  opponens digiti minimi

• (8) muscles act on the thumb, (4) are intrinsic to
  the hand (flexor pollicis brevis, opponens pollicis,
  abductor pollicis brevis, & adductor pollicis)
  extrinsic muscles are (extensor pollicis longus,
  extensor pollicis brevis, abductor pollicis longus,
  & flexor pollicis longus
  FUNCTION OF THE HAND
• Opposition is a movement by which the
  pulp surface of the thumb is placed squarely
  in contact with--or dramatically opposite to-
  the terminal pads of one or all of the
  remaining digits
• This mvt and the resultant manueverability
  of the thumb separate us from other
  primates: abduction, circumduction &
  rotation
  FUNCTION OF THE HAND
• Opposibility index = total length of thumb x
  100/total length of index finger
• A low index denotes a long first finger and
  a short thumb, in primates the mean values
  are between 40 and 65.
  – Orangutans mean = 40
  – humans mean = 60
  FUNCTION OF THE HAND
• What movement of the thumb separates Old
  World monkeys and apes from New World
  monkeys and prosimians?
• Which primates are closest to our
  opposibility factor? (apes, gorillas, baboons
  and mandrills)
MOVEMENTS OF THE HAND
• Thomas Ellis (1804-1878) noted that the
  true position of rest in the hand “lies
  somewhere about a mean between the
  ranges of easy movement” Explain?
• How did Ellis come to this description?
MOVEMENTS OF THE HAND
• Two Classes of Movement of the Hand
  – Prehensile movements: an object, fixed or free,
    is held by a gripping or pinching action
    between the digits and the palm
  – Nonprehensile movements: include pushing,
    lifting, tapping, and punching movements of
    the fingers
MOVEMENTS OF THE HAND
• There are two main patterns and two
  subsidiary prehensile patterns:
      Main
      • precision - thumb held against pulp (pulp to pulp)
      • power - thumb held against palm
      Subsidiary
      • hook - without thumb
      • scissors - without thumb
• The type of grip used is a function of the activity itself &
  does not depend on the shape or size of the object gripped.
MOVEMENTS OF THE HAND
• How is this generalization effected by very
  small or very large objects?
• Differentiate the prehensile patterns in Old
  World and New World Primates.
• Regarding tools, should function dictate
  design?
  FUNCTION OF THE HAND
• What did your observational experiment
  yield regarding the (4) grips?

								
To top