Origin: Lat. 2 tendons of FDP (as unipennate mm.)

Insertion: Lat. sides of DDE of 2nd and 3rd digits.

Action: Flex MCPs; extend IPs of 2nd-3rd digits.

Inervation: Median n. (C8, T1)

Origin: Med. 3 tendons of FDP (as bipennate mm.)

Insertion: Lat. side of DDE of 4th and 5th digits.

Action: Flex MCPs; extend IPs of 4th and 4th digits.

Inervation: Deep branch of ulnar n. (C8, T1)

Palmar Interossei

Palmar Adductors(PAD)

Origin: Palmar surfaces of 2nd, 4th and 5th metacarpals (Unipennate)

Insertion: Bases of proximal phalanges; DDE of 2nd, 4th and 5th digits.

Action: ADD 2nd, 4th and 5th digits; assists lumbricals in flexing MCPs

and extending IPs.

Inervation: Deep branch of ulnar n. (C8, T1).

Dorsal Interossei 

Dorsal Abductors (DAB)

Origin: Adjacent sides of two metacarpals (bipennate)

Insertion: Bases of proximal phalanges; DDE of 2nd-4th digits.

Action: ABD 2nd-4th digits; act with lumbricals in flexing MCPs and extending IPs.

Inervation: Deep branch ulnar n. (C8, T1).