For the muscle of the hand, see Lumbrical muscle (hand).

The lumbricals are four small skeletal muscle

Skeletal muscle

Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...

s, accessory to the tendons of the flexor digitorum longus

Flexor digitorum longus muscle

The Flexor digitorum longus is situated on the tibial side of the leg. At its origin it is thin and pointed, but it gradually increases in size as it descends...

 and numbered from the medial side of the foot; they arise from these tendons, as far back as their angles of division, each springing from two tendons, except the first.

The muscles end in tendon

Tendon

A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...

s, which pass forward on the medial sides of the four lesser toes, and are inserted into the expansions of the tendons of the Extensor digitorum longus on the dorsal surfaces of the first phalanges

Phalanx bones

In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...

. All four lumbricals insert into extensor hoods of the phalanges, thus creating extension at the inter-phalangeal joints. However as the tendons also pass inferior to the metatarsal phalangeal joints it creates flexion at this joint.

Variations

Absence of one or more; doubling of the third or fourth even the fifth. Insertion partly or wholly into the first phalanges.

Innervation

The most medial lumbrical is innervated by the medial plantar nerve

Medial plantar nerve

The medial plantar nerve , the larger of the two terminal divisions of the tibial nerve, accompanies the medial plantar artery....

 while the remaining three lumbricals are supplied by the lateral plantar nerve

Lateral plantar nerve

The lateral plantar nerve is a branch of the tibial nerve, in turn a branch of the sciatic nerve and supplies the skin of the fifth toe and lateral half of the fourth, as well as most of the deep muscles, its distribution being similar to that of the ulnar nerve in the hand.It passes obliquely...

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External links

• PTCentral