Lumbricals of the hand

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Lumbricals of the hand
Lumbricals of the hand.GIF
System: Muscle
Function: Flexion of the metacarpophalangeal joints and extension of the interphalangeal joints of the hand
Origin: Tendons of flexor digitorum profundus
Branches:
Insertion: Lateral side of extensor expansion of fingers
Arterial supply:
Venous drainage:
Lymphatic drainage:
Innervation: First and second:median nerve (C8, T1)
Third and fourth:deep terminal branch of the ulnar nerve (C8, T1)
Vertebral levels:
Search for Lumbricals of the hand in Gray's.

The lumbricals of the hand (lumbricals, lumbricales) are four short muscles of the fingers. They are notable for the differences between the lateral and medial pairs.

Contents

Shape

The lumbricals are four small muscles arising from the tendons of flexor digitorum profundus. The first and second are unipennate, arising from the anterolateral surfaces of their respective tendons, whilst the third and fourth are bipennate and arise from the adjoining sides of two adjacent tendons.

First lumbrical

The first lumbrical of the hand arises from the anterolateral surface of the tendon of flexor digitorum profundus to the index finger. It inserts on the lateral side of the extensor expansion of extensor digitorum above the metacarpophalangeal joint of the index finger.

Second lumbrical

The second lumbrical of the hand is a unipennate muscle arising from the anterolateral surface of the tendon of flexor digitorum profundus to the middle finger. It inserts on the lateral side of the extensor expansion of extensor digitorum above the metacarpophalangeal joint of the middle finger.

Third lumbrical

The third lumbrical of the hand is a bipennate muscle arising from the medial surface of the tendon of flexor digitorum profundus to the middle finger and the lateral surface of the tendon to the ring finger. It inserts on the lateral side of the extensor expansion of extensor digitorum above the metacarpophalangeal joint of the ring finger.

Fourth lumbrical

The fourth lumbrical of the hand is a bipennate muscle arising from the medial surface of the tendon of flexor digitorum profundus to the ring finger and the lateral surface of the tendon to the little finger. It inserts on the lateral side of the extensor expansion of extensor digitorum above the metacarpophalangeal joint of the little finger.

Actions

Joints Affected

Origin

First lumbrical:

Second lumbrical:

Third lumbrical:

Fourth lumbrical:

Insertion

First lumbrical:

Second lumbrical:

Third lumbrical:

Fourth lumbrical:

Nerve Supply

First and second:

Third and fourth:

Variations

  • May only be two lumbricals
  • May be five or six lumbricals
  • Insertions vary considerably

See Also

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