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The Palmar Interossei muscles are members of the Central Compartment Group of intrinsic muscles of the hand, composed of the:
- Adductor pollicis
- Lumbricals manus
- Palmar interossei
- Dorsal interossei manus
There are three Palmar Interossei muscles, named #1, #2, and #3, from radial/lateral (thumb side) to ulnar/medial (little finger side).
ATTACHMENTS:
- The palmar interossei attach from metacarpals #2, #4, and #5 to the proximal phalanges of fingers #2, #4, and #5 on the “middle-finger side.”
- Palmar interosseus #1 attaches onto finger #2 (index finger).
- Palmar interosseus #2 attaches onto finger #4 (ring finger).
- Palmar interosseus #3 attaches onto finger #5 (little finger).
- The palmar interossei also attach distally into the dorsal digital expansion.
ACTIONS:
- Adducts fingers #2, #4, #5 at the metacarpophalangeal joints.
- Flexes fingers #2, #4, #5 at the metacarpophalangeal joints.
- Extends fingers #2, #4, #5 at the proximal and distal interphalangeal joints.
NOTES:
- Because the palmar interossei attach onto their respective fingers on the “middle-finger side,” they bring those fingers toward the middle finger, which is defined as adduction.
- There is a mnemonic for remembering the abductors/adductors of the fingers: DAB PAD – Dorsals ABduct Palmars ADduct.