| A | B |
|---|
| mobility of the shoulder, wlbow and wrist, all operating in differnt planes, allows the hand to movee... | within large space volume |
| hand as ..bones and ...joints | 19 bones and 14 joints |
| elementary components of hands | fingers and thumb |
| bones of hand are arragnes in.. | three arches. |
| responsible for changing the shape of hand | extrinsic flexor and extensor muscles |
| responsible for maintaining the configuratino of arches | intrinsic muscles |
| as the fingers flex during a grasp, he longitudinal archess... | fold in a strict mathematical pattern (equiangular spiral) |
| hand grows.. | without changing shape in spite of its segmental length inequalities |
| great mobility of hand is due to | articular contours, the position of the bones in relation to one another and the actions of an intricate set of muscles |
| 2nd and 3rd metacarpals are linked to... | the trapezoid capitiate and to each other by tight-fitting joints that are basically immoblie (immobile unit of hand) |
| articulations of 4th and 5th metacarpals with the hamate | permit a modest amount of motion (10-15 degrees of F/E at the 4th CMC jiont and 20-30 degrees at 5th jiont) |
| the metacarpophalangeal joints (MCP) | are diarthrodial joints allowing motion in 3 planes: F/E, Ab/Ad, Pron/Sup |
| interphalangeal joints | larges range of motion occur at PIP joint (110or more degrees). proximal and distal ip jionts are bicondylar hinge jints as a result of tongue-and-groove fit of their articular surfaces. these surfaces are closely congruent throughout the range of F/E (only motion possilbe). extension beyond the zero position is a feature of the DIP and PIP joints (depends on ligament laxity) |
| base of thumb metacarpal forms.. | a saddle joint with the trapezium (allows a wide ROM) |
| most important function of the thumb | is opposition (abductin coupled with rotation of the CMC jiont; flexion at the MCP and IP joints brings thumb closer to fingertips) |
| dorsal tendinous complex (extensor assembly) | contributes to control and stability of IP joints |
| flexor tendon sheath pulley system | facilitates smooth and stable flexion at the IP joints |
| bony and ligamentous asymmetry of MCP joints | gives the hand functional versatility |
| all of the digital articulations have one essential feaute in common | they are designed to function in flexion |
| each joint has | collateral ligaments bilaterally and thick, reinforced anterior capsule |
| dorsal capsal is | thin and lax |
| palmar tendon apparatus | composed of two flexor tendons. is much stronger than dorsal extensor assebmly |
| most tendons in hand are...to some extent by....that keep them close to the skeletal plane to maintain | restricted, sheaths and retinacula, to maintain a realtively constant moment arm |
| as finger moves | each tendon slides a certain distance (excursion of tendon). agonist and antagonist tendon slide in opposite directions. strength of the finger flexors is twice that of extensors |
| degenerative jiont disease | jionts of human finger are geometrically and kinematically similar but refertial degerneration of the DIP is well documented. rheumatoid arthritis causes multiple deformities. |
| classic symptom of rheuamtoid arthritsis | ulnar drift. subluxating forces on the pulleys, ulnar deviation during a power grip. |
| another deformity besides ulnar drift caused by rheumatoid arthritis involes the... | PIP joint |
