Lumbricals of the hand

Source: Wikipedia, the free encyclopedia.
For the foot muscles, see
Lumbrical muscle of the foot
.
Lumbricals of the hand
interphalangeal joints
Identifiers
Latinmusculi lumbricales manus
TA98A04.6.02.065
TA22532
FMA37385
Anatomical terms of muscle]

The lumbricals are intrinsic

interphalangeal joints.[1][2]

The

lumbrical muscles of the foot
also have a similar action, though they are of less clinical concern.

Structure

The lumbricals are four, 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,[1][2][3] and distally to the extensor expansions.[1][3] The first and second lumbricals are unipennate, while the third and fourth lumbricals are bipennate.[2][4]

# Form Origin Insertion
First
unipennate
 It originates from the radial side of the most radial tendon of the flexor digitorum profundus (corresponding to the index finger). It passes posteriorly along the radial side of the index finger to insert on the extensor expansion near the metacarpophalangeal joint.
Second unipennate It originates from the radial side of the second most radial tendon of the flexor digitorum profundus (which corresponds to the middle finger). It passes posteriorly along the radial side of the middle finger and inserts on the extensor expansion near the metacarpophalangeal joint.
Third
bipennate
 One head originates on the radial side of the flexor digitorum profundus tendon corresponding to the ring finger, while the other originates on the ulnar side of the tendon for the middle finger. The muscle passes posteriorly along the radial side of the ring finger to insert on its extensor expansion.
Fourth bipennate One head originates on the radial side of the flexor digitorum profundus tendon corresponding to the little finger, while the other originates on the ulnar side of the tendon for the ring finger. The muscle passes posteriorly along the radial side of the little finger to insert on its extensor expansion.
Lumbricals labeled at bottom left. Left hand, palmar view.

Nerve supply

The first and second lumbricals (the most radial two) are innervated by the median nerve. The third and fourth lumbricals (most ulnar two) are innervated by the deep branch of ulnar nerve.[5]

This is the usual innervation of the lumbricals (occurring in 60% of individuals). However 1:3 (median:ulnar - 20% of individuals) and 3:1 (median:ulnar - 20% of individuals) also exist. The lumbrical innervation always follows the innervation pattern of the associated muscle unit of flexor digitorum profundus (i.e. if the muscle units supplying the tendon to the middle finger are innervated by the median nerve, the second lumbrical will also be innervated by the median nerve).[6]

Blood supply

Four separate sources supply blood to these muscles: the

common palmar digital artery, the deep palmar arch, and the dorsal digital artery.[7]

Function

The lumbrical muscles, with the help of the interosseous muscles, simultaneously flex the

interphalangeal joints
of the digit on which it inserts. The lumbricals are used during an upstroke in writing.

Etymology

The term "lumbrical" comes from the Latin, meaning "worm".[8]

Additional images

  • Tendons of forefinger and vincula tendina
    Tendons of forefinger and vincula tendina
  • Lumbricals of the hand
    Lumbricals of the hand
  • Lumbricals of the hand
    Lumbricals of the hand
  • Lumbricals muscle
    Lumbricals muscle
  • Lumbricals muscle
    Lumbricals muscle
  • Lumbricals muscle
    Lumbricals muscle
  • Lumbricals muscle
    Lumbricals muscle
  • Lumbricals muscle
    Lumbricals muscle
  • Muscles of hand, cross section
    Muscles of hand, cross section
  • Wrist joint. Deep dissection.Anterior, palmar view
    Wrist joint. Deep dissection.Anterior, palmar view
  • Wrist joint. Deep dissection.Anterior, palmar view
    Wrist joint. Deep dissection.Anterior, palmar view
  • Wrist joint. Deep dissection.Anterior, palmar view
    Wrist joint. Deep dissection.Anterior, palmar view

References

  1. ^
    ISBN 978-0-7234-3451-1
    . p. 97
  2. ^
    PMID 17825776
    .
  3. ^
    PMID 24369943
    .
  4. S2CID 244111
    .
  5. S2CID 8084761
    .
  6. ISBN 978-0-443-05611-6
    .
  7. S2CID 26384944
    .
  8. S2CID 81678124
    .
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