Lumbricals of the hand | |
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Details | |
Origin | Flexor digitorum profundus |
Insertion | Extensor expansion |
Artery | Superficial palmar arch, common palmar digital arteries, deep palmar arch, dorsal digital artery |
Nerve | Third and fourth deep branch of ulnar nerve, first and second median nerve |
Actions | Flex metacarpophalangeal joints, extend interphalangeal joints |
Identifiers | |
Latin | musculi lumbricales manus |
TA98 | A04.6.02.065 |
TA2 | 2532 |
FMA | 37385 |
Anatomical terms of muscle |
The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints, [1] and extend the interphalangeal joints. [1] [2]
The lumbrical muscles of the foot also have a similar action, though they are of less clinical concern.
The lumbricals are four, 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, [1] [2] [3] and distally to the extensor expansions. [1] [3] The first and second lumbricals are unipennate, while the third and fourth lumbricals are bipennate. [2] [4]
# | Form | Origin | Insertion |
First | unipennate | It originates from the radial side of the most radial tendon of the flexor digitorum profundus (corresponding to the index finger). | It passes posteriorly along the radial side of the index finger to insert on the extensor expansion near the metacarpophalangeal joint. |
Second | unipennate | It originates from the radial side of the second most radial tendon of the flexor digitorum profundus (which corresponds to the middle finger). | It passes posteriorly along the radial side of the middle finger and inserts on the extensor expansion near the metacarpophalangeal joint. |
Third | bipennate | One head originates on the radial side of the flexor digitorum profundus tendon corresponding to the ring finger, while the other originates on the ulnar side of the tendon for the middle finger. | The muscle passes posteriorly along the radial side of the ring finger to insert on its extensor expansion. |
Fourth | bipennate | One head originates on the radial side of the flexor digitorum profundus tendon corresponding to the little finger, while the other originates on the ulnar side of the tendon for the ring finger. | The muscle passes posteriorly along the radial side of the little finger to insert on its extensor expansion. |
The first and second lumbricals (the most radial two) are innervated by the median nerve. The third and fourth lumbricals (most ulnar two) are innervated by the deep branch of ulnar nerve. [5]
This is the usual innervation of the lumbricals (occurring in 60% of individuals). However 1:3 (median:ulnar - 20% of individuals) and 3:1 (median:ulnar - 20% of individuals) also exist. The lumbrical innervation always follows the innervation pattern of the associated muscle unit of flexor digitorum profundus (i.e. if the muscle units supplying the tendon to the middle finger are innervated by the median nerve, the second lumbrical will also be innervated by the median nerve). [6]
Four separate sources supply blood to these muscles: the superficial palmar arch, the common palmar digital artery, the deep palmar arch, and the dorsal digital artery. [7]
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. The lumbricals are used during an upstroke in writing.
The term "lumbrical" comes from the Latin, meaning "worm". [8]
The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus.
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers. It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Flexor digitorum superficialis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints.
In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar aspect of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.
The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting and manipulating objects.
The extensor digitorum muscle is a muscle of the posterior forearm present in humans and other animals. It extends the medial four digits of the hand. Extensor digitorum is innervated by the posterior interosseous nerve, which is a branch of the radial nerve.
The flexor pollicis longus is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is unique to humans, being either rudimentary or absent in other primates. A meta-analysis indicated accessory flexor pollicis longus is present in around 48% of the population.
In human anatomy, the palmar or volar interossei are four muscles, one on the thumb that is occasionally missing, and three small, unipennate, central muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers. They are smaller than the dorsal interossei of the hand.
In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from hand's midline and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle and ring fingers.
In human anatomy, the abductor digiti minimi is a skeletal muscle situated on the ulnar border of the palm of the hand. It forms the ulnar border of the palm and its spindle-like shape defines the hypothenar eminence of the palm together with the skin, connective tissue, and fat surrounding it. Its main function is to pull the little finger away from the other fingers.
The deep transverse metacarpal ligament connects the palmar surfaces of metacarpophalangeal joints of all the fingers of the hand except the thumb.
The anterior interosseous nerve is a branch of the median nerve that supplies the deep muscles on the anterior of the forearm, except the ulnar (medial) half of the flexor digitorum profundus. Its nerve roots come from C8 and T1.
In the human body, the carpal tunnel or carpal canal is a flattened body cavity on the flexor (palmar/volar) side of the wrist, bounded by the carpal bones and flexor retinaculum. It forms the passageway that transmits the median nerve and the tendons of the extrinsic flexor muscles of the hand from the forearm to the hand. There are described cases of the anatomical variant median artery occurrence.
The muscles of the hand are the skeletal muscles responsible for the movement of the hand and fingers. The muscles of the hand can be subdivided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm. The intrinsic group are the smaller muscles located within the hand itself. The muscles of the hand are innervated by the radial, median, and ulnar nerves from the brachial plexus.
An ulnar claw, also known as claw hand or ‘Spinster’s Claw’, is a deformity or an abnormal attitude of the hand that develops due to ulnar nerve damage causing paralysis of the lumbricals. A claw hand presents with a hyperextension at the metacarpophalangeal joints and flexion at the proximal and distal interphalangeal joints of the 4th and 5th fingers. The patients with this condition can make a full fist but when they extend their fingers, the hand posture is referred to as claw hand. The ring- and little finger can usually not fully extend at the proximal interphalangeal joint (PIP).
The hand of benediction, also known as benediction sign or preacher's hand, has been said to occur as a result of prolonged compression or injury of the median nerve at the forearm or elbow.
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.
Injuries to the arm, forearm or wrist area can lead to various nerve disorders. One such disorder is median nerve palsy. The median nerve controls the majority of the muscles in the forearm. It controls abduction of the thumb, flexion of hand at wrist, flexion of digital phalanx of the fingers, is the sensory nerve for the first three fingers, etc. Because of this major role of the median nerve, it is also called the eye of the hand. If the median nerve is damaged, the ability to abduct and oppose the thumb may be lost due to paralysis of the thenar muscles. Various other symptoms can occur which may be repaired through surgery and tendon transfers. Tendon transfers have been very successful in restoring motor function and improving functional outcomes in patients with median nerve palsy.
The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles allow for flexion, extension, adduction, abduction and opposition of the thumb. The muscles acting on the thumb can be divided into two groups: The extrinsic hand muscles, with their muscle bellies located in the forearm, and the intrinsic hand muscles, with their muscles bellies located in the hand proper.
Palmaris profundus is a rare anatomical variant in the anterior compartment of forearm. It was first described in 1908. It is usually found incidentally in cadaveric dissection or surgery.