Antebrachium Extensors

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Antebrachium Extensors
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Extensor retinaculum

• thick fibrous fascia band at wrist -holds forearm
  tendons in place
• from lateral radius to medial ulna (styloid
  process), triquetrum pisiform bones

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Extensor Canals

• six osteofibrous canals post side of bones
• extensor tendons pass through to dorsal hand

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Extensor Canals

• a. abductor pollicis longus, \ extensor
  pollicis brevis / in 1 most lateral
• b. extensor carpi radialis longus \ extensor
  carpi radialis brevis / in 2
• c. extensor pollicis longus - in 3
• d. extensor digitorum \ extensor indicis / in
  4
• e. extensor digiti minimi - in 5
• f. extensor carpi ulnaris - in 6

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Anatomical snuff box

• depression on dorsolateral wrist bounded by
  tendons of
• abductor pollicis longus, extensor pollicis
  brevis extensor pollicis longus (where the
  scaphoid bone lies in the floor here, most likely
  be fractured, local tenderness, death
  absorption of the bone later)

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Muscles

• Muscles 3 Functional groups brachioradialis
  supinator
• i) extend hand at wrist the 3 extensor carpi's
  - radialis longus brevis ulnaris
• ii) extend medial 4 digits (fingers) extensors
  digitorum indicis digiti minimi
• iii) extend thumb (1st digit) abductor pollicis
  longus extensor pollicis longus brevis

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Muscles

• Extensor are arranged in three anatomical layers
• Superficial layer
• brachioradialis
• extensor carpi radialis longus
• extensor carpi radialis brevis
• extensor digitorum
• extensor digiti minimi
• extensor carpi ulnaris

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BRACHIORADIALIS

• ORIGINproximal two thirds of lateral
  supracondylar ridge of humerus, and lateral
  intermuscular septum
• INSERTIONlateral side of base of styloid process
  of radius
• ACTIONflex the elbow joint, and assists in
  pronating and supinating the forearm when these
  movements are resisted
• NERVEradial nerve C5, C6

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EXTENSOR CARPI RADIALIS LONGUS

• ORIGINDistal one third of lateral supracondylar
  ridge of humerus, and lateral intermuscular
  septum
• INSERTIONdorsal surface of base of second
  metacarpal bone, radial side
• ACTIONextends and abducts the wrist, and assists
  in flexion of the elbow
• NERVEradial nerve C5, C6, 7, 8

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EXTENSOR CARPI RADIALIS BREVIS

• ORIGINcommon extensor tendon from lateral
  epicondyle of humerus, radial collateral ligament
  of elbow joint, and deep antebrachial fascia
• INSERTIONdorsal surface of base of third
  metacarpal bone
• ACTIONextends and assists in abduction of the
  wrist
• NERVEradial C6, 7, 8

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EXTENSOR DIGITORUM

• ORIGINCommon extensor tendon fromlateral
  epicondyle of humerus, and deep antebrachial
  fascia
• INSERTIONBy four tendons, each penetrating a
  membranous expansion on the dorsum of the second
  to fifth digits and dividing over the proximal
  phalanx into medial and two lateral bands. The
  medial band inserts into the base of the middle
  phalanx while the lateral bands reunite over the
  middle phalanx and insert into the base of the
  distal phalanx.
• ACTIONExtends the metacarpophalangeal and, in
  conjunction with the lumbricals and interossei,
  extends the interphalangeal joints of the second
  through fifth digits. Assists in abduction of the
  index, ring, and little fingers and assists in
  extension and abducting of the wrist.
• NERVERadial nerve, C6, 7, 8

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EXTENSOR DIGITI MINIMI

• ORIGINCommon extensor tendon from lateral
  epicondyle of humerus, and deep antebrachial
  fascia
• INSERTIONInto extensor expansion of little
  finger with extensor digitorum tendon
• ACTIONExtends the metacarpophalangeal joint and,
  in conjunction with lumbricals interosseus,
  extends the interphalangeal joints of the little
  finger. Assists in abduction of the little finger
• NERVEradial nerve C6, 7, C8

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EXTENSOR CARPI ULNARIS

• ORIGINCommon extensor tendon fromlateral
  epicondyle of humerus, by aponeurosis from
  posterior border of ulna, and deep antebrachial
  fascia
• INSERTIONbase of fifth metacarpal bone, ulnar
  side
• ACTIONextends and adducts the wrist
• NERVEradial nerve C6, 7, C8  

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Deep layer

• Supinator
• abductor pollicis longus
• extensor pollicis brevis
• extensor pollicis longus
• extensor indicis

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SUPINATOR

• ORIGINLateral epicondyle of humerus, radial
  collateral ligament of elbow joint, annular
  ligament of radius, and superior crest of ulna
• INSERTIONLateral surface of upper one third of
  body of radius covering part of anterior and
  posterior surfaces
• ACTIONsupinates the forearm
• NERVEradial nerve C5, C6, C(7)

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ABDUCTOR POLLICIS LONGUS

• ORIGINposterior surface of body of ulna distal
  to origin of supinator, interosseus membrane, and
  posterior surface of middle one third of body of
  radius
• INSERTIONbase of first metacarpal bone, radial
  side
• ACTIONAbducts and extends the carpometacarpal
  joints of the thumb abducts (radial deviation)
  and assists in flexion the wrist
• NERVERadial nerve C6, 7, C8

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EXTENSOR POLLICIS BREVIS

• ORIGINPosterior surface of body of radius distal
  to origin of abductor pollicis longus, and
  interosseus membrane
• INSERTIONBase of proximal phalanx of thumb,
  dorsal surface
• ACTIONExtends the metacarpophalangeal joint of
  the thumb, extends and abducts the
  carpometacarpal joint, and assists in abduction
  (radial deviation) of the wrist
• NERVERadial nerve C6, 7, C8 

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EXTENSOR POLLICIS LONGUS

• ORIGINMiddle one third of posterior surface of
  ulna distal to origin of abductor pollicis
  longus, and interosseus membrane
• INSERTIONBase of distal phalanx of thumb, dorsal
  surface
• ACTIONExtends the interphalangeal joint and
  assists in extension of the metacarpophalangeal
  and carpometacarpal joints of the thumb. Assists
  in abduction and extension of the wrist.
• NERVERadial nerve, C6,  C7, C8 

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EXTENSOR INDICIS

• ORIGINposterior surface of body of ulna distal
  to origin of extensor pollcis longus, and
  interosseus membrane.
• INSERTIONInto extensor expansion of index finger
  with extensor digitorium longus tendon
• ACTIONExtends the metacarpophalangeal joint and,
  in conjunction with the  lumbricals and
  interossei, extends the interphalangeal joints of
  the index finger. May assist in adduction of the
  finger
• NERVERadial nerve C6, 7, C8