The lumbricals are four small

skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...

s, accessory to the tendons of the flexor digitorum longus muscle. They are numbered from the medial side of the foot.

Structure

The lumbricals arise from the tendons of the flexor digitorum longus muscle, as far back as their angles of division, each springing from two tendons, except the first. The first lumbrical is unipennate, while the second, third and fourth are bipennate. The muscles end in

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

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 muscle on the dorsal surfaces of the proximal

phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...

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

Innervation

The most medial lumbrical is innervated by the medial plantar nerve while the remaining three lumbricals are supplied by the lateral plantar nerve.

Variation

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

History

The term "lumbrical" comes from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, meaning "

worm Worms are many different distantly related bilateria, bilateral animals that typically have a long cylindrical tube-like body, no limb (anatomy), limbs, and usually no eyes. Worms vary in size from microscopic to over in length for marine ...

Additional images

File:1124 Intrinsic Muscles of the Foot c.png, The lumbricals of the foot flex the metatarsophalangeal joints and extend the interphalangeal joints.

References

External links

PTCentral
Foot muscles Muscles of the lower limb {{muscle-stub