Third lumbrical muscle

Origin: Flexor digitorum profundus

Insertion: Extensor expansion

Artery: Superficial palmar arch, common palmar digital arteries, deep palmar arch, dorsal digital artery

Nerve: Deep branch of ulnar nerve, median nerve

Action: Flex metacarpophalangeal joints, extend interphalangeal joints

Description:
The Lumbricales are four small fleshy fasciculi, associated with the tendons of the Flexor digitorum profundus. The first and second arise from the radial sides and volar surfaces of the tendons of the index and middle fingers respectively; the third, from the contiguous sides of the tendons of the middle and ring fingers; and the fourth, from the contiguous sides of the tendons of the ring and little fingers. Each passes to the radial side of the corresponding finger, and opposite the metacarpophalangeal articulation is inserted into the tendinous expansion of the Extensor digitorum communis covering the dorsal aspect of the finger.

Variations.—The Lumbricales vary in number from two to five or six and there is considerable variation in insertions.