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WRIST AND HAND ANATOMY

Bones
Muscles
Joints and ligaments


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BONY ANATOMY


 - Three main groups of bones constitute the skeleton of the hand. 
 - From proximal to distal, these include the carpal bones, metacarpal
   bones, and the phalanges .
 - Additionally, the hand also contains some small bony structures 
   termed sesamoid bones. 

 Carpal bones 
 - The hand contains 8 carpal bones made up of 2 rows of 4 bones 
   each. 
 - From lateral to medial, the proximal row consists of the scaphoid, 
   lunate, triquetrum, and pisiform bones. In the same order, the distal
   row consists of the trapezium, trapezoid, capitate, and hamate bones. 
 - The anterolateral margins of the scaphoid and trapezium elevate and
   protrude forward to make an attachment site for the flexor 
   retinaculum. 
 - The hamate bone has a bony hook volarly, and the pisiform stands 
   on the triquetrum; thus, these 2 protrusions provide the medial 
   attachment side for the flexor retinaculum. 
 - The distal row of the carpal bones joins to the metacarpal bones to 
   form the carpometacarpal joint. The carpus is cartilaginous at 
   birth. 
 - The capitate begins to ossify during the first year, and the others 
   begin to ossify at intervals thereafter until the 12th year, when
   all bones are ossified. 

 Metacarpal bones 
 - The hand has 5 metacarpal bones. 
 - From proximal to distal, each has a base, a shaft, and a head. 
 - The first metacarpal bone constitutes the skeleton of the thumb 
   and is the shortest and most mobile. It is in contact with the 
   trapezium proximally. 
 - The other 4 metacarpals contact with the trapezoid, capitate and 
   hamate, and lateral-medial surfaces of metacarpal bones. The heads
   of the metacarpal bones, which form the knuckles, articulate with
   the proximal phalanges.
 - The shaft of each metacarpal bone is slightly concave forward 
   and is triangular in transverse section, with medial, lateral, and
   posterior surfaces. 

 Phalanges 
 - The hand has 14 phalanges.
 - Each finger contains 3 phalanges, but each thumb only has 2.
 - The hand contains some complex joints, including, from proximal
   to distal order, the radiocarpal, intercarpal, carpometacarpal, 
   MCP, and interphalangeal joints. 

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MUSCLES OF THE WRIST AND HAND



 - The hand is multitalented - it can perform powerful grasping tasks 
   as well as delicate ones. 
 - The large, forceful muscles for the former have their proximal 
   attachments in the arm and forearm in order to achieve the desired 
   angle of pull. 
 - They attach to appropriate parts of the hand and wrist by means of 
   long tendons, but their muscle bellies and origins are far from the 
   hand - hence the designation "extrinsic". 
 - Intrinsic muscles are small and are entirely confined to the
   region distal to the long bones of the forearm.
 - Keeping track of all these muscles is made simpler by grouping 
   them according to where they are, what they do, or both. 
 - The forearm has the convenient dividing line of its 2 long bones 
   (radius and ulna) and the strong interosseous membrane that 
   connects them. 
 - The muscles on the volar side are said to lie in the anterior 
   compartment, and generally flex or pronate the hand. They can be 
   envisioned as being in 3 groups- superficial, middle, and deep. 
 - Muscles on the dorsal side of the interosseous membrane are said
   to lie in the posterior compartment, and generally extend or 
   supinate the hand. 
 - They can be further subdivided according to their actions (acting on 
   the wrist joint, fingers, or thumb). 
 - The intrinsic muscles can be grouped according to the digit they 
   move. 
 - Thenar muscles affect the thumb, hypothenar muscles the 5th or
   little finger, and "short finger muscles" affect mostly digits 2-5 
   (index finger- little finger).

·Anterior compartment (flexor-pronator group) 
    1. Superficial 
    2. Middle 
    3. Deep 

· Posterior compartment (extensor-supinator group) 
    4. Wrist-level hand motion 
    5. Finger motion 
    6. Thumb motion 

 Intrinsic muscles
    1. thenar group 
    2. Hypothenar group 
    3. Short finger muscles

 Superficial muscles of the anterior compartment

1. PRONATOR TERES
    ORIGIN: Humeral head: medial epicondyle, medial supracondylar 
       ridge and medial intermuscular septum. Ulnar head: medial 
       border of coronoid process	 
    INSERTION: Just posterior to most prominent part of lateral 
       convexity of radius	
    ACTION: Pronates forearm and flexes elbow	
    NERVE: Median nerve (C6,7) (from lateral and medial cords)	

2. FLEXOR CARPI RADIALIS
    ORIGIN: Common flexor origin of medial epicondyle of humerus	 
    INSERTION: Bases of 2nd and 3rd metacarpals via groove in
       trapezium and slip to scaphoid	
    ACTION: Flexes and abducts wrist	
    NERVE: Median nerve (C6, 7) (from medial and lateral cords)	

3. PALMARIS LONGUS
    ORIGIN: Common flexor origin of medial epicondyle of humerus	 
    INSERTION: Flexor retinaculum and palmar aponeurosis	
    ACTION: Flexes wrist and tenses palmar aponeurosis	
    NERVE: Median nerve (C7, 8) (from medial and lateral cords)	

4. FLEXOR CARPI ULNARIS
    ORIGIN: Humeral head: common flexor origin of medial epicondyle.
       Ulnar head: aponeurosis from medial olecranon and upper 
       three quarters subcutaneous border of ulna	 
    INSERTION: Pisiform, hook of hamate, base of 5th metacarpal via
       pisohamate and pisometacarpal ligaments 	
    ACTION: Flexes and adducts wrist. Fixes pisiform during action 
       of hypothenar muscles	
    NERVE: Ulnar nerve (C6, 7) (by communication from lateral cord)	

middle muscle of anterior compartment

1.FLEXOR DIGITORUM SUPERFICIALIS
    ORIGIN: Humeral head: common flexor origin of medial epicondyle
       humerus, medial ligament of elbow. Ulnar head: medial border
       of coronoid process and fibrous arch. Radial head: whole 
       length of anterior oblique line	 
   INSERTION: Tendons split to insert onto sides of middle phalanges
      of medial four fingers	
    ACTION: Flexes proximal interphalangeal joints and secondarily
      metacarpophalangeal joints and wrist	
    NERVE: Median nerve (C7, 8) (from medial and lateral cords) 	

Deep 3 muscles of the anterior compartment
 
1. FLEXOR POLLICIS LONGUS
    ORIGIN: Anterior surface of radius below anterior oblique line
       and adjacent interosseous membrane 	 
    INSERTION: Base of distal phalanx of thumb	
    ACTION: Flexes distal phalanx of thumb	
    NERVE: Anterior interosseous nerve (C7, 8)	

2. FLEXOR DIGITORUM PROFUNDUS
    ORIGIN: Medial olecranon, upper three quarters of anterior and
       medial surface of ulna as far round as subcutaneous border and 
       narrow strip of interosseous membrane 	 
    INSERTION: Distal phalanges of medial four fingers. Tendon to 
       index finger separates early 	
    ACTION: Flexes distal interphalangeal joints, then secondarily
      flexes proximal interphalangeal and metacarpophalangeal joints 
      and wrist	
    NERVE: Median nerve (anterior interosseous) (C6, 7) / ulnar
      nerve (C7, 8) 	

3. PRONATOR QUADRATUS
    ORIGIN: Lower quarter of anteromedial shaft of ulna	 
    INSERTION: Lower quarter of anterolateral shaft of radius and 
      some interosseous membrane	
    ACTION: Pronates forearm and maintains ulna and radius opposed	
    NERVE: Anterior interosseous nerve (C8)	

    Muscles of the posterior compartment that act 
       on the hand at the wrist joint

1. EXTENSOR CARPI RADIALIS LONGUS
    ORIGIN: Lower third of lateral supracondylar ridge of humerus 
       and lateral intermuscular septum 	 
    INSERTION: Posterior base of 2nd metacarpal	
    ACTION: Extends and abducts hand at wrist 	
    NERVE:Radial nerve (C6, 7) 	

2. EXTENSOR CARPI RADIALIS BREVIS
    ORIGIN: Common extensor origin on anterior aspect of lateral 
    epicondyle of humerus 	 
    INSERTION: Posterior base of 3rd metacarpal	
    ACTION: Extends and abducts hand at wrist 	
    NERVE: Posterior interosseous nerve (C7, 8) 	

 3. EXTENSOR CARPI ULNARIS
    ORIGIN: Common extensor origin on anterior aspect of lateral
       epicondyle of humerus 	 
    INSERTION: Base of 5th metacarpal via groove by ulnar styloid 	
    ACTION: Extends and adducts hand at wrist 	
    NERVE: Posterior interosseous 	

Muscles of the posterior compartment that act on the fingers (digits 2-5)

1. EXTENSOR DIGITORUM
    ORIGIN: Common extensor origin on anterior aspect of lateral 
       epicondyle of humerus 	 
    INSERTION: External expansion to middle and distal phalanges 
       by four tendons. Tendons 3 and 4 usually fuse and little finger
       just receives a slip 	
    ACTION: Extends all joints of fingers 	
    NERVE: Posterior interosseous nerve (C7, 8) 	

2. EXTENSOR INDICIS
    ORIGIN: Lower posterior shaft of ulna (below extensor pollicis 
        longus) and adjacent interosseous membrane	 
    INSERTION: Extensor expansion of index finger (tendon lies on
        ulnar side of extensor digitorum tendon)	
    ACTIONExtends all joints of index finger	
    NERVEPosterior interosseous nerve (C7, 8)	

3. EXTENSOR DIGITI MINIMI
    ORIGIN: Common extensor origin on anterior aspect of lateral
       epicondyle of humerus 	 
    INSERTION: Extensor expansion of little finger-usually two tendons
      which are joined by a slip from extensor digitorum at 
      metacarpophalangeal joint 	
    ACTION: Extends all joints of little finger	
    NERVE: Posterior interosseous nerve (C7, 8) 	

Muscles of the posterior compartment that act on the thumb 
                (digit 1)

1. ABDUCTOR POLLICIS LONGUS
    ORIGIN: Upper posterior surface of ulna and middle third of 
      posterior surface of radius and interosseous membrane 
      between 	 
    INSERTION: Over tendons of radial extensors and brachioradialis
      to base of 1st metacarpal and trapezium 	
    ACTION: Abducts and extends thumb at carpometacarpal joint	
    NERVE: Posterior interosseous nerve (C6, 7)	

 2. EXTENSOR POLLICIS BREVIS
    ORIGIN: Lower third of posterior shaft of radius and adjacent
       interosseous membrane 	 
    INSERTION: Over tendons of radial extensors and brachioradialis 
       to base of proximal phalanx of thumb 	
    ACTION: Extends metacarpophalangeal joint of thumb	
    NERVE: Posterior interosseous nerve (C7, 8) 	

3. EXTENSOR POLLICIS LONGUS
    ORIGIN: Middle third of posterior ulna (below abductor pollicis
       longus) and adjacent interosseous membrane	 
    INSERTION: Base of distal phalanx of thumb via Lister's tubercle 
      (dorsal tubercle of radius).	
    ACTION: Extends interphalangeal and metacarpophalangeal joints
      of thumb	
    NERVE: Posterior interosseous nerve (C7 , 8 ) 	

Intrinsic muscles of the hand - thenar group

1. OPPONEN POLLICIS
    ORIGIN: Flexor retinaculum and tubercle of trapezium	 
    INSERTION: Whole of radial border of 1st metacarpal	
    ACTION: Opposes (medially rotates and flexes ) carpometacarpal
      and metacarpophalangeal joints of thumb	
    NERVE: Recurrent (muscular) branch of median nerve (C8,T1)
      ( may also be from deep branch of ulnar nerve (T1))	

2. ABDUCTOR POLLICIS BREVIS
     ORIGIN: Tubercle of scaphoid & flexor retinaculum 	 
     INSERTION: Radial sesamoid of proximal phalanx of thumb & 
       tendon of extensor pollicis longus 	
     ACTION: Abducts thumb at metacarpophalangeal & 
       carpometacarpal joints 	
     NERVE: Recurrent (muscular) branch of median nerve(C8, T1) 
        occasionally by ulnar nerve	

3. FLEXOR POLLICIS BREVIS
     ORIGIN: Flexor retinaculum and tubercle of trapezium	 
     INSERTION: Base of proximal phalanx of thumb (via radial 
        sesamoid)	
     ACTION: Flexes metacarpophalangeal joint of thumb	
     NERVE: Recurrent (muscular) branch of median nerve (C8, T1)
        (may also be from deep branch of ulnar nerve (T1))	

4. ADDUCTOR POLLICIS
     ORIGIN: Oblique head: base of 2nd and 3rd metacarpals, trapezoid
         and capitate. Transverse head: palmar border and shaft of 3rd
         metacarpal	 
     INSERTION: Ulnar sesamoid then ulnar side of base of proximal
         phalanx and tendon of extensor pollicis longus	
     ACTION: Adducts carpometacarpal joint of thumb	
     NERVE: Deep branch of ulnar nerve (T1) 	

Intrinsic muscles of the hand - hypothenar group

1. ABDUCTOR DIGITI MINIMI (hand)
    ORIGIN: Pisiform bone, pisohamate ligament and flexor retinaculum 	 
    INSERTION: Ulnar side of base of proximal phalanx of little 
        finger and extensor expansion	
    ACTION: Abducts little finger at metacarpophalangeal joint 	
    NERVE: Deep branch of ulnar nerve (C8, T1)	


2. FLEXOR DIGITI MINIMI BREVIS
     ORIGIN: Flexor retinaculum and hook of hamate	 
     INSERTION: Ulnar side of base of proximal phalanx of little 
         finger 	
     ACTION: Flexes metacarpophalangeal joint of little finger	
     NERVE: Deep branch of ulnar nerve (C8, T1)	

3. OPPONEN DIGITI MINIMI HAND
     ORIGIN: Flexor retinaculum and hook of hamate	 
     INSERTION: Ulnar border of shaft of 5th metacarpal	
     ACTION: Opposes (flexes and laterally rotates) carpometacarpal
       and metacarpophalangeal joints of little finger	
     NERVE: Deep branch of ulnar nerve (C8, T1)	

Intrinsic muscles of the hand — short finger muscles

1. LUMBRICALS
     ORIGIN: Four tendons of flexor digitorum profundus. 
        Radial 2: radial side only (unipennate). 
        Ulnar 2: cleft between tendons ( bipennate)	 
     INSERTION: Extensor expansion (dorsum of proximal phalanx ) 
        of fingers 2-5 radial side	
     ACTION: Flex metacarpophalangeal joints and extend
        interphalangeal joints of fingers	
     NERVE: Lateral 2: median nerve (C8, T1). medial 2: deep branch 
        of ulnar nerve (C8, T1)	

2. DORSAL INTEROSSEI
     ORIGIN: Bipennate from inner aspects of shafts of all metacarpals	 
      INSERTION: Proximal phalanges and dorsal extensor expansion 
          on radial side of index and middle fingers and ulnar side of 
          middle and ring fingers 	
      ACTION: Abduct from axis of middle finger. Flex 
         metacarpophalangeal joint while extending interphalangeal 
         joints 	
      NERVE: Deep branch of ulnar nerve (T1) 	

3. PALMAR INTEROSSEI
      ORIGIN: Anteriorshafts of 1, 2, 4, 5 metacarpals (unipennate)	 
      INSERTION: Proximal phalanges and dorsal extensor expansion 
          on ulnar side of index and radial side of ring and little
          fingers and to ulnar sesamoid of thumb	
      ACTION: Adduct to axis of middle finger. Flex 
         metacarpophalangeal joint while extending interphalangeal
          joints	
      NERVE: Deep branch of ulnar nerve (T1)	


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JOINTS AND LIGAMENTS OF THE HAND


Radiocarpal joint 
 - This joint constitutes the distal articular surfaces of the radius 
   and the scaphoid, lunate, and triquetral bones. 
 - An articular disk is present between the distal and proximal 
   osteal structures. 
 - The proximal articular surface has a shallow depression, and the
   distal articular surface has a fitting protrusion. 
 - The type of joint is synovial spheroid. 
 - The capsule of the joint encloses it and includes the articular 
    cartilaginous structures. 
 - Radial and ulnar collateral ligaments strengthen both sides of the 
   joint. 
 - Palmar and dorsal radiocarpal ligaments cover the back and 
   front of the wrist joint. 
 - The anterior interosseous nerve and a deep branch of the radial 
   nerve innervate it.
 - The main movements of the wrist joint are flexion, extension,
   abduction, and adduction. 
 - They can move in circumduction when a combination of these
    movements is used. 

Intercarpal joints 
 - An intercarpal joint occurs between the distal and proximal row of
   the carpal bones and between every individual carpal bone.
 -  It is a synovial and plane-type joint. 
 - The articular capsule surrounds these structures. 

Carpometacarpal joints 
 - An intercarpal joint occurs between the distal and proximal row 
   of the carpal bones and between every individual carpal bone. 
 - It is a synovial and plane-type joint. 
 - The articular capsule surrounds these structures. 

Metacarpophalangeal joints 
 - The 5 MCP joints are located between the head of the metacarpal 
   bones and the base of the proximal phalanges. 
 - They are synovial condyloid joints surrounded by a synovial 
   capsule. 
 - The capsule is pliable in the front and back and rigid on the sides.
 - MCP joints can flex, extend, abduct, and adduct. 
 - Using a combination of these movements, they can move in 
   restricted circumduction. 
 - Strong and tight palmar and collateral ligaments support the joints
   volarly, radially, and ulnarly. 
 - Additionally, the deep transverse metacarpal ligaments connect
   the medial 4 joints to each other and hold the head of the 
   metacarpal bones together. 

Interphalangeal joints 
 - These are located between the phalanges and are synovial hinge 
  joints. 
 - Palmar and collateral ligaments support the joints in the front and 
   sides. 
 - Interphalangeal joints can be flexed or extended

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