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Dorsal Interossei


- See: Intrinsic Muscles of the Hand;

- Origin: each from the 2 metacarpal bones between which it inserts;
- Insertion:
    - superficial belly:
         - inserts onto the lateral tubercle at the base of the proximal phalanx (proximal phalanges of 2nd, 3rd, and 4th digits) 
                to function as an abductor;
    - deep belly: inserts onto the lateral tendon to help form the lateral band of the radial three fingers;

- Action: the 1st abducts the index finger, the 2nd radially flexes the
    - middle finger, 3rd flexes middle finger & 4th abducts ring finger;
    - all assists in flexing proximal phalanges of the index, middle and ring fingers at metacarpophalangeal joints;
- Nerve supply: palmar branch of the Ulnar  nerve, C8 ,   T1
- Synergists: lumbrical, Palmar Interossei, Flexor Digitorum ProfundusFlexor Digitorum Superficialis

- First Dorsal Interosseous:
    - largest of the interossei;
    - origin: inner borders of first and second metacarpals;
    - passes dorsal to adductor pollicis;
    - insertion: extensor expansion mechanism on dorsum of finger;

- Summary:
    - 1st, 2nd, and 4th, dorsal interossei - 2 muscle bellies:
    - one of which inserts on the base ofthe proximal phalanx;
    - one of which inserts on the dorsal aponeurosis;
    - 3rd dorsal interosseous and all 3 volar interossei insert on to only dorsal aponeurosis;

  Opponensplasty in intrinsic-muscle paralysis of the thumb in leprosy.

  Patterns of movement of totally intrinsic-minus fingers based on a study of one hundred and forty-one fingers.

  Movement patterns of interosseus-minus fingers.

  Abductor pollicis longus transfer for replacement of first dorsal interosseous.

 Architectural design of the human intrinsic hand muscles.