MBS 212 Human Movement

1. MBS 212 Human Movement Lecture 6 Forearm and hand movements 2/2 Prof. Thomas K. Monsees 2008 Prof. Monsees

2. Summary: Muscles of the Forearm Prof. Monsees

3. Hand • Hand is subdivided into 3 parts • Wrist • Metacarpus • Digits (5 fingers including thumb) • Fingers form flexed arcade in resting position, stretched in anatomical position • Palm = anterior surface, Dorsum = dorsal surface of hand • Hand is mechanical + sensory tool • Many features of upper limb are designed to facilitate positioning of hand in space Prof. Monsees

4. Abduction and adduction of fingers are defined with respect to long axis of middle finger • In anatomical pos, long axis of thumb is rotated 90 deg to rest of the digits so that pad of thumb points medially movements of thumb are defined at right angels to movements of the other digits Prof. Monsees

5. Bones of the hand • 3 groups of bones • 8 carpal bones • 5 metacarpals (metacarpus) • Phalanges (3 per digits, 2 per thumb) • Carpal bones + metacarpals of digits 2-5 tend to function as a unit, form bony framework of palm • Metacarpal bone of thumb functions independently, has increased flexibility at carpometacarpal joint, can provide opposition of thumb Prof. Monsees

6. Carpal bones Prof. Monsees

7. Carpal bones forming arch Carpal bones do not lie in flat plane; rather they form an arch Prof. Monsees

8. Carpal tunnel Prof. Monsees

9. Carpal tunnel (cont…) • Structures passing the tunnel: • 4 tendons of flexor digitorium profundus • 4 tendons of flexor digitorium superficialis • Tendon of flexor pollicis longus • Median nerve • Structure passing flexor retinaculum • Tendon of flexor carpi radialis is surrounded by synovial sheath and passes through tubular compartment formed by lat aspect of flexor retinaculum Prof. Monsees

10. Flexor retinaculum • Thick connective tissue ligament that bridges space between med + lat sides of the arch • Thus converting carpal arch into carpal tunnel • Flexor retinaculum holds the tendons to bony plane at wrist and prevents them from ‘bowing’ Prof. Monsees

11. Palmar aponeurosis • Triangular shaped condensation of deep fascia that covers the palm • Apex is continous with tendon of palmaris longus + anchored to flexor retinaculum • From here, fibers radiate to extensions of base of the digits • Transverse fibers interconnect the more longitudinally arranged bundles • Vessels, nerves + long flexor tendons lie deep to the palmar aponeurosis Flexor retinaculum Tendon palmaris longus Prof. Monsees

12. Fibrous digital sheaths Deep transverse metacarpal ligament Synovial sheath • After existing the carpal tunnel, tendons of flexors cross the palm and enter fibrous sheaths • They are formed by fibrous arches + cross-shaped ligaments • They holds the tendons to bony plane and prevent tendons from bowing when digits are flexed • Within each tunnel, the tendons are surrounded by a synovial sheath Fibrous digital sheaths Synovial sheath Flexor retinaculum Prof. Monsees

13. Extensor hoods • Tendons of extensor digitorium and extensor pollices longus muscles pass onto dorsal aspect of digits and expand over proximal phalanges to form complex extensor hoods or dorsal digital expansions • Tendons of other extensor muscles will also join these hoods Prof. Monsees

14. Extensor hood (cont…) • Many of the intrinsic muscle of the hand insert the hood • They are responsible for complex delicate movements of digits that could not be done with the long tendons alone • Force from intrinsic muscles is applied to hood distal to fulcrum of metacarpophalangeal joint  muscles flexed the joint Contraction of intrinsic muscles Prof. Monsees

15. Anatomical snuffbox • Triangular depression formed by posterolateral side of wrist • Historically, ground tabocco (snuff) was placed here before being inhaled by nose • Important clinical region: • When hand is in ulnar deviation, the scaphoid becomes palpable within the snuff box. This enables the physician to palpate the bone to assess a fracture. • Pulse of radial artery can also be felt here Prof. Monsees

16. Extrinsic vs. Intrinsic Muscles Extrinsic muscles of the hand • Originate at the forearm • Insert in the hand • Function in forcefully gripping (power grip) Intrinsic muscles • Occur entirely in the hand • Manly execute precise movements (precision grip) Prof. Monsees

17. More muscles of the hand… Intrinsic muscles • Adductor pollicis • Interossei • Thenar group • Hypothenar group • Palmaris brevis • Lumbrical Prof. Monsees

18. Dorsal Interossei Dorsal interossei (palmar view) • 4 bipennate muscles between and attached to shafts of metacarpal bones • Major abductors of the index, middle + ring fingers • In addition: Flexing + extension of 2,3,4 fingers • Thumb + little finger do not have dorsal interossei Prof. Monsees

19. Palmar Interossei Palmar interossei (palmar view) • 4 unipennate palmar muscles anterior located to the dorsal interossei • Adduct thumb, index, ring + little finger Prof. Monsees

20. Adductor pollices • Transverse + oblique head • Powerful adductor of thumb • Opposes thumb to rest of digits in gripping Prof. Monsees

21. 3 Thenar muscles  thumb movement • Opponens pollicis • Flexor pollicis brevis • Abductor pollicis brevis • Opposes thumbto rest of digits + delicate movement of thumb • Responsible for thenar eminence: prominent swelling on lat side of palm at base of thumb • Innervated by recurrent branch of median nerve Abductor pollicis brevis Opponens pollicis Flexor pollicis brevis Prof. Monsees

22. 3 Hypothenar muscles  little finger movement Hypothenar muscles are similar to the thenar regarding name and organization • Opponens digiti minimi: • Rotates metacarpal 5 towards palm (little finger) • Flexor digiti minimi • Flexes metacarpophalangeal joint (little finger) • Abductor digiti minimi • Principal abductor of little finger • Responsible for hypothenar eminence: prominent swelling on med side of palm at base of little finger • Innervated by deep branch of ulnar nerve Prof. Monsees

23. 3 Hypothenar muscles Opponens digiti minimi Abductor digiti minimi Flexor digiti minimi Prof. Monsees

24. Lumbrical muscles • 4 Worm-like muscles, each of which associated with one of the fingers • Muscles originates from tendons of flexor digitorium profundus • Lumbricals are unique: they mix flexor with extensor tendons • 2 medial associated with middle + ring + little finger • 2 lateral associated with index + middle finger Prof. Monsees

25. Thank you for your attention! • Next week L7 • Upper limb joints Prof. Monsees