Lumbricals of the hand

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For the foot muscles, see Lumbrical muscle of the foot.
Lumbricals of the hand
Lumbricales (hand).png
The muscles of the left hand. Palmar surface. (1st lumbricalis labeled at bottom right of muscular group.)
Details
Latin musculi lumbricales manus
flexor digitorum profundus
extensor expansion
superficial palmar arch, common palmar digital arteries, deep palmar arch, dorsal digital artery
3rd and 4th deep branch of ulnar nerve, 1st and 2nd median nerve
Actions flex metacarpophalangeal joints, extend interphalangeal joints
Identifiers
Gray's p.464
Dorlands
/Elsevier
m_22/12549749
TA A04.6.02.065
FMA FMA:37385
Anatomical terms of muscle

The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints and extend the interphalangeal joints.[1]

Structure[edit]

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 the extensor expansions.[1]

# 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.

Innervation[edit]

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 the ulnar nerve.

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).[2]

Blood supply[edit]

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[edit]

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[edit]

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

Additional images[edit]

Tendons of forefinger and vincula tendina 
Lumbricals of the hand 
]Lumbricals of the hand 
Lumbricals muscle 
Lumbricals muscle 
Lumbricals muscle 
Lumbricals muscle 
Lumbricals muscle 
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. 

Notes[edit]

  1. ^ a b Gosling et al. 2008, p. 97
  2. ^ Last's Anatomy - Regional and Applied, 10th ed. Chummy S. Sinnatamby, pg. 64 and pg. 82.

References[edit]

  • Gosling, J.A.; Harris, P.F.; Humpherson, J.R.; Whitmore, I.; Willan, P.L.T. (2008). Human Anatomy: Color Atlas and Textbook. phot. by A.L. Bentley (5th ed.). Philadelphia: Mosby. ISBN 978-0-7234-3451-1.