Lumbrical

Lumbrical

The lumbrical muscles are intrinsic muscles of the hand and foot. They are unique in that they do not attach directly to bone but rather to tendons. These muscles play a crucial role in the fine motor movements of the fingers and toes.

Anatomy

Hand

In the hand, there are four lumbrical muscles. They originate from the tendons of the flexor digitorum profundus and insert into the extensor expansions of the fingers. The lumbricals are numbered from one to four, starting from the radial (thumb) side to the ulnar (little finger) side.

• First and Second Lumbricals: These are unipennate muscles, meaning they have fibers on one side of the tendon. They originate from the lateral two tendons of the flexor digitorum profundus.
• Third and Fourth Lumbricals: These are bipennate muscles, meaning they have fibers on both sides of the tendon. They originate from the medial three tendons of the flexor digitorum profundus.

Foot

In the foot, there are also four lumbrical muscles. They originate from the tendons of the flexor digitorum longus and insert into the extensor expansions of the toes.

• First Lumbrical: This muscle is unipennate and originates from the medial side of the first tendon of the flexor digitorum longus.
• Second to Fourth Lumbricals: These muscles are bipennate and originate from the adjacent sides of the tendons of the flexor digitorum longus.

Function

The primary function of the lumbrical muscles is to flex the metacarpophalangeal joints and extend the interphalangeal joints of the fingers and toes. This action is essential for tasks that require precision grip and fine motor control, such as writing or picking up small objects.

Innervation

The lumbrical muscles of the hand are innervated by the median nerve and the ulnar nerve. Specifically:

• The first and second lumbricals are innervated by the median nerve.
• The third and fourth lumbricals are innervated by the ulnar nerve.

The lumbrical muscles of the foot are innervated by the medial plantar nerve and the lateral plantar nerve.

Blood Supply

The blood supply to the lumbrical muscles in the hand comes from the superficial palmar arch and the deep palmar arch. In the foot, the blood supply is provided by the medial plantar artery and the lateral plantar artery.

Clinical Significance

Dysfunction of the lumbrical muscles can lead to difficulties in performing fine motor tasks. Conditions such as carpal tunnel syndrome can affect the median nerve, leading to weakness or paralysis of the first and second lumbricals. Similarly, injuries to the ulnar nerve can impact the third and fourth lumbricals.

Related Pages

• Flexor digitorum profundus
• Flexor digitorum longus
• Median nerve
• Ulnar nerve
• Medial plantar nerve
• Lateral plantar nerve
• Superficial palmar arch
• Deep palmar arch
• Medial plantar artery
• Lateral plantar artery
• Carpal tunnel syndrome