| Lumbricals of the hand | |
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| The muscles of the left hand. Palmar surface. (1st lumbricalis labeled at bottom right of muscular group.) | |
| Latin | musculi lumbricales manus |
| Gray's | subject #126 464 |
| Origin | flexor digitorum profundus |
| Insertion | extensor expansion |
| Artery | superficial palmar arch, common palmar digital arteries, deep palmar arch, dorsal digital artery |
| Nerve | 3rd and 4th deep branch of ulnar nerve, 1st and 2nd median nerve |
| Actions | flex metacarpophalangeal joints, extend interphalangeal joints |
The lumbrical muscles are intrinsic muscles in the fingers that allow flexion at the metacarpophalangeal joints, while maintaining extension at the interphalangeal joints.
Contents |
Structure
There are four of these small, worm-like muscles on each hand. These muscles are unusual in that they do not attach to bone. Instead they attach proximally to the tendons of flexor digitorum profundus and distally to extensor expansions on the dorsal surface (back) of the hand.
| # | Form | Origin | Insertion |
| first | unipennate | It originates from the lateral side of the most lateral tendon of the flexor digitorum profundus (corresponding to the index finger). | It passes posteriorly along the lateral side of the index finger to insert on the extensor expansion near the metacarpophalangeal joint. |
| second | unipennate | It originates from the lateral side of the second most lateral tendon of the flexor digitorum (which corresponds to the middle finger). | It passes posteriorly along the lateral side of the middle finger and inserts on the extensor expansion near the metacarpophalangeal joint. |
| third | bipennate | One head originates on the lateral side of the flexor digitorum profundus tendon corresponding to the ring finger, while the other originates on the medial side of the tendon for the middle finger. | The muscle passes posteriorly along the lateral side of the ring finger to insert on its extensor expansion. |
| fourth | bipennate | One head originates on the lateral side of the flexor digitorum profundus tendon corresponding to the little finger, while the other originates on the medial side of the tendon for the ring finger. | The muscle passes posteriorly along the lateral side of the little finger to insert on its extensor expansion. |
Innervation
The first and second lumbricals (i.e. the two that are most lateral) are innervated by the median nerve. The third and fourth lumbricals (i.e. the most medial two) are innervated by the deep branch of the ulnar nerve.
Blood supply
There are four separate sources of blood supply for these muscles: the superficial palmar arch, the common palmar digital artery, the deep palmar arch, and the dorsal digital artery.
Actions
The lumbrical muscles, with the help of the interosseous muscles, simultaneously flex the metacarpophalangeal joints while extending both interphalangeal joints of the digit on which it inserts. The lumbricals are used during an upstroke in writing.
Other lumbricals
There are also lumbrical muscles of the foot that have a similar action, though these are of less clinical concern.
Additional images
 Tendons of forefinger and vincula tendina. |
External links
- LUC lumh
- lumbrical+muscles+of+hand at eMedicine Dictionary
- Mnemonic at medicalmnemonics.com 5
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