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Origins, insertions, innervation and function of the lumbrical muscles of the hand.
Hi there! It’s Matt from Kenhub, and in this tutorial, we will discuss the lumbrical muscles of the hand. The lumbrical muscles are four short muscles of the hand located in the metacarpus deep to the palmar fascia. Fun fact: Lumbricidae is Latin for earthworm.
One feature of these muscles is that they originate from tendons instead of bony structures making their origin surfaces quite moveable. Usually, they arise from the radial side of the tendons of the flexor digitorum profundus. In addition, the third and fourth lumbrical muscles have a second head attached to the ulnar side of the adjacent tendon.
Distally, their insertion tendons attach to the dorsal aponeurosis of the respective finger. The first and second lumbricals are innervated by the median nerve whereas the ulnar nerve is responsible for the innervation of the third and fourth lumbricals.
The lumbricals fulfill movements of the second to fifth finger. Their contraction leads to flexion in the metacarpophalangeal joints and extension in both the proximal and distal interphalangeal joints. The reason for the opposite actions is that the tendons cross the metacarpophalangeal joints on the palmar side but distally insert at the dorsal side of the finger. These combined movements support a strong hand grip use, for example, to hold a pen.
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