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Lumbricals of the hand

For the foot muscles, see Lumbrical muscle of the foot

Lumbricals of the hand

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:	deep branch of ulnar nerve, median nerve
Action:	flex metacarpophalangeal joints, extend interphalangeal joints
Dorlands/Elsevier	m_22/12549749

The lumbrical muscles are intrinsic muscles in the fingers that allow flexion at the metacarpophalangeal joints, while maintaining extension at the interphalangeal joints.

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1 Structure
2 Innervation
3 Blood supply
4 Actions
5 Other lumbricals
6 Additional images

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.

Other lumbricals

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

Additional images

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Lumbricals_of_the_hand". A list of authors is available in Wikipedia.