Lumbricals of hand
The lumbricals of hand consist of four intrinsic muscles of the fingers that originate from the tendon of the digitorum profundus. These muscles are distinctive for the differentiation between the medial and lateral pairs. Of the four lumbricals, the first two are unipennate, originating from their respective tendons. The remaining two are bipennate, originating from the side of the two adjoining tendons. The first of these muscles arises from the digitorum profundus tendon to the index finger. It inserts on the lateral portion of the extensor digitorum. The second muscle goes to the middle finger. The third goes to the ring finger. Lastly, the fourth goes to the little finger. The first and second muscles are innervated by the median nerve; the ulnar nerve innervates the third and fourth muscles. The lumbricals of hand receive blood supply from four different sources. These include the dorsal digital artery, the superficial and deep palmar arches, and the palmar digital artery. The lumbricals of hand perform the key function of flexing the metacarpophalangeal joints with support from the interosseous muscles.