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Origin of Superficial Head: Flexor retinaculum and trapezium bone
Origin of Deep Head: Trapezoid and capitate bones

Insertion: Base of proximal phalanx of thumb, radial side, and extensor expansion.

Innervation: Nerve to Superficial Head: Median, C6, 7, 8, T1. Nerve to Deep Head: Ulnar, C8, T1. 

Action: Flexes the MCP and flexes and adducts the CMC joints of the thumb, and assists in opposition of the thumb toward the little finger.