Lumbricals of the hand

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For the foot muscles, see Lumbrical muscle of the foot

Lumbricals of the hand
Image:Lumbricales (hand).png
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.

Contents 1 Structure 2 Innervation 3 Blood supply 4 Actions 5 Other lumbricals 6 Additional images 7 External links

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

Tendons of forefinger and vincula tendina.

External links

• LUC lumh
• lumbrical+muscles+of+hand at eMedicine Dictionary
• Mnemonic at medicalmnemonics.com 5

v • d • e List of muscles of upper limbs
VERTEBRAL COLUMN	trapezius - latissimus dorsi - rhomboid (major, minor) - levator scapulae
THORACIC WALLS	pectoralis major - pectoralis minor - subclavius - serratus anterior
SHOULDER	deltoid - rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis) - teres major
ARM	anterior compartment: coracobrachialis - biceps brachii - brachialis posterior compartment: triceps brachii - anconeus
FOREARM	anterior compartment: superf. - pronator teres - palmaris longus - flexor carpi radialis - flexor carpi ulnaris - flexor digitorum superficialis anterior compartment: deep - pronator quadratus - flexor digitorum profundus - flexor pollicis longus posterior compartment: superf. - mobile wad (brachioradialis, extensor carpi radialis longus and brevis) - extensor digitorum, - extensor digiti minimi - extensor carpi ulnaris posterior compartment: deep - supinator - anatomical snuff box (abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus) - extensor indicis
HAND	lateral volar - thenar (opponens pollicis, flexor pollicis brevis, abductor pollicis brevis) - adductor pollicis medial volar - hypothenar (opponens digiti minimi, flexor digiti minimi brevis, abductor minimi digiti) - palmaris brevis intermediate - lumbrical - interossei (dorsal, palmar)

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