Palmar Interossei

• Palmar Interossei:

  • 4 unipennate muscles

  
• O (origin):

  • Palmar surfaces of 1st (often rudimentary), 2nd, 4th and 5th metacarpal shafts

  A) Palmar Interossei

  
• R (direction):

  • Distally

  A) Palmar Interossei

  
• I (insertion):

  • Dorsal digital expansions and bases of proximal phalanges of digits (1), 2, 4 and 5

  A) Palmar Interossei

  
• A (action):

  • Adduction and flexion of metacarpophalangeal joints
  • Extension of interphalangeal joints (through dorsal digital expansion)

  A) Palmar Interossei

  
• NS (nerve supply):

  • Deep branch ulnar nerve (C7 - T1)

  A) Palmar Interossei

  
• Remember:

  • palmar interossei assist with adduction
  • 3rd finger doesnt adduct
  • so the muscles are only present on the 1st, 2nd, 4th and 5th fingers