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Finger
The fingers of a left hand seen from both sides
Details
Identifiers
Latindigiti manus
MeSHD005385
TA98A01.1.00.030
TA2150
FMA9666
Anatomical terminology

A finger is a prominent digit on the forelimbs of most tetrapod vertebrate animals, especially those with prehensile extremities (i.e. hands) such as humans and other primates. Most tetrapods have five digits (pentadactyly),[1][2] and short digits (i.e. significantly shorter than the metacarpal/metatarsals) are typically referred to as toes, while those that are notably elongated are called fingers. In humans, the fingers are flexibly articulated and opposable, serving as an important organ of tactile sensation and fine movements, which are crucial to the dexterity of the hands and the ability to grasp and manipulate objects.

Humans

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Usually humans have five digits,[3] the bones of which are termed phalanges,[2] on each hand, although some people have more or fewer than five due to congenital disorders such as polydactyly or oligodactyly, or accidental or intentional amputations. The first digit is the thumb, followed by the index finger, middle finger, ring finger, and little finger or pinkie. According to different definitions, the thumb can be called a finger, or not.

English dictionaries describe finger as meaning either one of the five digits including the thumb, or one of the four digits excluding the thumb (in which case they are numbered from 1 to 4 starting with the index finger closest to the thumb).[1][2][4]

Structure

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Skeleton

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Illustration depicting the bones of the human hand

The thumb (connected to the trapezium) is located on one of the sides, parallel to the arm.

The palm has five bones known as metacarpal bones, one to each of the five digits. Human hands contain fourteen digital bones, also called phalanges, or phalanx bones: two in the thumb (the thumb has no middle phalanx) and three in each of the four fingers. These are the distal phalanx, carrying the nail, the middle phalanx, and the proximal phalanx. Joints are formed wherever two or more of these bones meet. Each of the fingers has three joints:

  • metacarpophalangeal joint (MCP) – the joint at the base of the finger
  • proximal interphalangeal joint (PIP) – the joint in the middle of the finger
  • distal interphalangeal joint (DIP) – the joint closest to the fingertip.

Sesamoid bones are small ossified nodes embedded in the tendons to provide extra leverage and reduce pressure on the underlying tissue. Many exist around the palm at the bases of the digits; the exact number varies between different people.

The articulations are: interphalangeal articulations between phalangeal bones, and metacarpophalangeal joints connecting the phalanges to the metacarpal bones.

Muscles

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The precision of finger movements in space and time is highlighted in this motion tracking of two pianists' fingers playing the same piece (slow motion, no sound).[5]

Each finger may flex and extend, abduct and adduct, and so also circumduct. Flexion is by far the strongest movement. In humans, there are two large muscles that produce flexion of each finger, and additional muscles that augment the movement. The muscle bulks that move each finger may be partly blended, and the tendons may be attached to each other by a net of fibrous tissue, preventing completely free movement. Although each finger seems to move independently, moving one finger also moves the other fingers slightly which is called finger interdependence or finger enslaving.[6][7][8]

Fingers do not contain muscles (other than arrector pili). The muscles that move the finger joints are in the palm and forearm. The long tendons that deliver motion from the forearm muscles may be observed to move under the skin at the wrist and on the back of the hand.

Muscles of the fingers can be subdivided into extrinsic and intrinsic muscles. The extrinsic muscles are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm.

The fingers have two long flexors, located on the underside of the forearm. They insert by tendons to the phalanges of the fingers. The deep flexor attaches to the distal phalanx, and the superficial flexor attaches to the middle phalanx. The flexors allow for the actual bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group. The human thumb also has other muscles in the thenar group (opponens and abductor brevis muscle), moving the thumb in opposition, making grasping possible.

The extensors are located on the back of the forearm and are connected in a more complex way than the flexors to the dorsum of the fingers. The tendons unite with the interosseous and lumbrical muscles to form the extensorhood mechanism. The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm; the tendons of these form the anatomical snuff box. Also, the index finger and the little finger have an extra extensor, used for instance for pointing. The extensors are situated within six separate compartments. The first compartment contains abductor pollicis longus and extensor pollicis brevis. The second compartment contains extensors carpi radialis longus and brevis. The third compartment contains extensor pollicis longus. The extensor digitorum indicis and extensor digitorum communis are within the fourth compartment. Extensor digiti minimi is in the fifth, and extensor carpi ulnaris is in the sixth.

The intrinsic muscle groups are the thenar and hypothenar muscles (thenar referring to the thumb, hypothenar to the small finger), the dorsal and palmar interossei muscles (between the metacarpal bones) and the lumbrical muscles. The lumbricals arise from the deep flexor (and are special because they have no bony origin) and insert on the dorsal extensor hood mechanism.

Skin

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Aside from the genitals, the fingertips possess the highest concentration of touch receptors and thermoreceptors among all areas of the human skin,[9] making them extremely sensitive to temperature, pressure, vibration, texture and moisture. A study in 2013 suggested fingers can feel nano-scale wrinkles on a seemingly smooth surface, a level of sensitivity not previously recorded.[10] This makes the fingers commonly used sensory probes to ascertain properties of objects encountered in the world, making them prone to injury.

The pulp of a finger is the fleshy mass on the palmar aspect of the extremity of the finger.[11]

Fingertip wrinkling in water

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Although a common phenomenon, the underlying functions and mechanism of fingertip wrinkling following immersion in water are relatively unexplored. Originally it was assumed that the wrinkles were simply the result of the skin swelling in water,[12] but it is now understood that the furrows are caused by the blood vessels constricting due to signalling by the sympathetic nervous system in response to water exposure.[13][14] One hypothesis for why this occurs, the "rain tread" hypothesis, posits that the wrinkles may help the fingers grip things when wet, possibly being an adaption from a time when humans dealt with rain and dew in forested primate habitats.[13] A 2013 study supporting this hypothesis found that the wrinkled fingertips provided better handling of wet objects but gave no advantage for handling dry objects.[15] However, a 2014 study attempting to reproduce these results was unable to demonstrate any improvement of handling wet objects with wrinkled fingertips.[14]

Regrowth of the fingertips

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Fingertips, after having been torn off children, have been observed to regrow in less than 8 weeks.[16] However, these fingertips do not look the same, although they do look more appealing than a skin graft or a sewn fingertip. No healing occurs if the tear happens below the nail. This works because the distal phalanges are regenerative in youth, and stem cells in the nails create new tissue that ends up as the fingertip.[17]

Brain representation

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Each finger has an orderly somatotopic representation on the cerebral cortex in the somatosensory cortex area 3b,[18] part of area 1[19] and a distributed, overlapping representations in the supplementary motor area and primary motor area.[20]

The somatosensory cortex representation of the hand is a dynamic reflection of the fingers on the external hand: in syndactyly people have a clubhand of webbed, shortened fingers. However, not only are the fingers of their hands fused, but the cortical maps of their individual fingers also form a club hand. The fingers can be surgically divided to make a more useful hand. Surgeons did this at the Institute of Reconstructive Plastic Surgery in New York to a 32-year-old man with the initials O. G.. They touched O. G.'s fingers before and after surgery while using MRI brain scans. Before the surgery, the fingers mapped onto his brain were fused close together; afterward, the maps of his individual fingers did indeed separate and take the layout corresponding to a normal hand.[21]

Clinical significance

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Anomalies, injuries and diseases

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Radiograph of Type 1 Syndactyly

A rare anatomical variation affects 1 in 500 humans, in which the individual has more than the usual number of digits; this is known as polydactyly. A human may also be born without one or more fingers or underdevelopment of some fingers such as symbrachydactyly. Extra fingers can be functional. One individual with seven fingers not only used them but claimed that they "gave him some advantages in playing the piano".[22]

Phalanges are commonly fractured. A damaged tendon can cause significant loss of function in fine motor control, such as with a mallet finger. They can be damaged by cold, including frostbite and non-freezing cold injury (NFCI); and heat, including burns.

The fingers are commonly affected by diseases such as rheumatoid arthritis and gout. Individuals with diabetes often use the fingers to obtain blood samples for regular blood sugar testing. Raynaud's phenomenon and Paroxysmal hand hematoma are neurovascular disorders that affect the fingers.

Research has linked the ratio of lengths between the index and ring fingers to higher levels of testosterone, and to various physical and behavioral traits such as penis length[23] and risk for development of alcohol dependence[24] or video game addiction.[25]

Land vertebrates

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Fingers of a tree frog (amphibian)
Fingers of a red-eyed crocodile skink (reptile)
Red squirrel holding food with its fingers (mammal)
Fingers of a bat (mammal)

As terrestrial vertebrates were evolved from lobe-finned fish, their forelimbs are phylogenetically equivalent to the pectoral fins of fish. Within the taxa of the terrestrial vertebrates, the basic pentadactyl plan, and thus also the metacarpals and phalanges, undergo many variations.[26] Morphologically the different fingers of terrestrial vertebrates are homolog. The wings of birds and those of bats are not homologous, they are analogue flight organs. However, the phalanges within them are homologous.[27]

Chimpanzees have lower limbs that are specialized for manipulation, and (arguably) have fingers (instead of toes) on their lower limbs as well. In the case of primates in general, the digits of the hand are overwhelmingly referred to as "fingers".[28][29] Primate fingers have both fingernails and fingerprints.[30]

Research has been carried out on the embryonic development of domestic chickens showing that an interdigital webbing forms between the tissues that become the toes, which subsequently regresses by apoptosis. If apoptosis fails to occur, the interdigital skin remains intact. Many animals have developed webbed feet or skin between the fingers from this like the Wallace's flying frog.[31][32][33]

Etymology

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The English word finger stems from Old English finger, ultimately from Proto-Germanic *fingraz ('finger'). It is cognate with Gothic figgrs, Old Norse fingr, or Old High German fingar. Linguists generally assume that *fingraz is a ro-stem deriving from a previous form *fimfe, ultimately from Proto-Indo-European *pénkʷe ('five').[34]

The name pinkie derives from Dutch pinkje, of uncertain origin. In English only the digits on the hand are known as fingers. However, in some languages the translated version of fingers can mean either the digits on the hand or feet. In English a digit on a foot has the distinct name of toe.

See also

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Notes

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Finger

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from Grokipedia
A finger is one of the terminal digits of the hand or foot in vertebrates, particularly referring to the four digits excluding in humans. In human , each finger consists of three elongated bones called phalanges—proximal, middle, and distal—connected by hinge joints that allow flexion and extension, supported by muscles, tendons, ligaments, and a rich network of nerves and blood vessels for sensory and motor functions. , often distinguished, has only two phalanges. Fingers play crucial roles in grasping, manipulating objects, and fine motor tasks, varying across in structure and number for to different environments.

Fingers in Vertebrates

Structure and Variation

In vertebrate anatomy, a finger refers to one of the terminal digits of a tetrapod limb, particularly the manus (forelimb), composed of successive phalangeal bones articulated by synovial joints that enable flexion and extension. These phalanges form the distal portion of the autopodium (hand or foot), distal to the metacarpals, and typically include a proximal phalanx articulating with the metacarpal at the metacarpophalangeal joint, followed by one or more intermediate phalanges, and terminating in a distal phalanx often supporting a claw, hoof, or nail. This segmented structure provides flexibility and strength, with joints reinforced by collateral ligaments and capsules for stability during movement. The archetypal pentadactyl limb pattern, ancestral to crown-group tetrapods, features five digits per manus and pes, each with a characteristic phalangeal formula—commonly 2-3-4-5-3 for the manus in basal forms—reflecting a conserved developmental blueprint originating around 360 million years ago. The metacarpals, five elongated bones in the palm, serve as the proximal base, articulating with the carpals proximally and the proximal phalanges distally to form a supportive framework for digit mobility. However, phalangeal counts and overall digit structure vary widely due to evolutionary adaptations; for instance, many mammals maintain five digits with a simplified formula of 2-3-3-3-3, while some exhibit reductions or fusions, such as in equids where lateral digits are vestigial, leaving a single robust central digit for weight-bearing. Across land vertebrates, digit number and composition show class-specific diversity: most amphibians, like anurans, retain five digits but with variations such as four in forelimbs (phalangeal 2-2-3-2), suited to aquatic-terrestrial transitions; reptiles typically preserve five digits, though some like fuse them into flipper-like structures; birds reduce to three functional digits in the ( 2-3-4), with phalanges shortened and fused for aerodynamic efficiency. These variations on the pentadactyl theme—often involving loss, fusion, or elongation of phalanges—support specialized functions in locomotion, such as in moles or perching in birds, while maintaining homology traceable to early ancestors. In land vertebrates, fingers generally contribute to terrestrial by enabling propulsion, prey capture, or object manipulation, with the pentadactyl arrangement optimizing versatility on uneven substrates.

Functions

Fingers, or digits, in vertebrates serve diverse biomechanical roles in , manipulation, and environmental interaction, enabling adaptations to specific ecological niches. In , digits facilitate prehensile grasping, allowing precise manipulation of objects and support during , a key evolutionary trait that enhanced foraging and predator avoidance in tree-dwelling ancestors. In subterranean mammals like moles, robust foredigits are specialized for digging, with shovel-like shapes and an additional pseudo-thumb derived from a that increases surface area for excavating soil efficiently. For birds, hind digits enable perching by wrapping around branches, utilizing a tendon-locking mechanism that maintains grip with minimal muscular effort during rest or while roosting. Sensory integration through mechanoreceptors in digits provides critical tactile feedback for and across . These low-threshold mechanoreceptors, such as Merkel cells and Meissner corpuscles, detect vibrations, textures, and pressures, informing precise movements in environments ranging from forest floors to underwater substrates. This feedback loop supports adaptive behaviors, like probing for prey in star-nosed moles or substrate exploration in pectoral fins, highlighting the ancient origins of digit-based somatosensation in . Opposability of digits is a prominent in arboreal animals, where the hallux or pollex can flex to oppose other digits, forming a secure clamp for trunks and branches, as seen in and certain marsupials. In contrast, ungulates exhibit load-bearing digits evolved for terrestrial support, with progressive reduction to a single weight-bearing in equids, enhancing speed and stability on open plains through fused phalanges that distribute compressive forces effectively. Evolutionary derivations include claws in carnivores for traction and prey capture, and hooves in as keratinized expansions of nails, both originating from ancestral pentadactyl limbs to optimize force transmission in predatory or grazing lifestyles. Biomechanically, phalangeal joints provide leverage for force application, acting as fulcrums where flexor tendons generate to amplify or . In grasping tasks, curved phalanges increase moment arms, allowing efficient force distribution without excessive muscle energy, a principle conserved across vertebrates from limbs to mammalian paws. This configuration, varying with habitat demands, underscores how digit morphology translates neural commands into adaptive mechanical outputs.

Human Finger Anatomy

Skeletal and Muscular Structure

The skeletal structure of the human finger consists of elongated long bones known as phalanges, which form the primary framework for digit mobility. Each of the four fingers (index, middle, ring, and little) features three phalanges: the proximal phalanx, adjacent to the metacarpal; the middle phalanx; and the distal phalanx at the fingertip. In contrast, contains only two phalanges—a proximal and a distal—allowing for greater opposability and . These phalanges articulate with the at their bases, where the metacarpal heads form the foundation for the metacarpophalangeal joints. As long bones, phalanges exhibit a diaphysis composed primarily of dense compact bone for structural strength and epiphyses of spongy bone to support and reduce weight. The joints of the human finger enable precise and coordinated movements essential for grasping and manipulation. The metacarpophalangeal (MCP) joints, located between the metacarpals and proximal phalanges for fingers 2 through 5, are condyloid synovial joints that permit flexion, extension, abduction, and adduction, with limited circumduction. The proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints, situated between the phalanges, function as (ginglymus) synovial joints, primarily allowing flexion and extension in a single plane to facilitate bending and straightening. These joint types are stabilized by collateral ligaments and volar plates, ensuring stability during fine motor tasks. Musculature of the human finger is divided into extrinsic and intrinsic groups, providing both power and precision. Extrinsic muscles originate in the and control gross movements via long tendons: the flexor digitorum superficialis inserts on the middle to flex , while the flexor digitorum profundus inserts on the distal to flex the DIP and, secondarily, . Intrinsic muscles, located entirely within the hand, enable fine adjustments; the lumbricals flex the MCP joints while extending the interphalangeal , and the palmar and dorsal interossei abduct and the fingers relative to the middle finger's axis. Tendons of these muscles glide smoothly within synovial sheaths—fibro-osseous tunnels that extend from the metacarpal necks to the distal phalanges—and are guided by a pulley system of five annular pulleys (A1–A5) and three pulleys (C1–C3), which prevent bowstringing and maintain mechanical efficiency during flexion. Blood supply to the human finger structures arises from the digital arteries, which are paired vessels branching from the radial and ulnar arteries via the superficial and deep palmar arches, ensuring nutrient delivery to bone, muscle, and tendons. Innervation is provided by the median and ulnar nerves: the median nerve supplies motor function to the extrinsic flexors (via anterior interosseous branch) and intrinsic lumbricals (first and second), while the ulnar nerve innervates the hypothenar muscles, interossei, and third and fourth lumbricals, with both nerves contributing to sensory digital branches.

Skin, Nails, and Sensory Features

The covering the human , particularly on the palmar (volar) surface, consists of thick glabrous lacking hair follicles and characterized by a prominent for durability and protection against mechanical stress. This glabrous features friction ridges, also known as fingerprints, formed by epidermal invaginations over dermal papillae, which enhance grip by increasing surface friction during object manipulation. The dermal papillae, as upward projections of the into the epidermis, amplify tactile sensitivity by expanding the interface for distribution and nutrient supply, adapting the for precise dexterity in fine motor tasks. Human fingernails are rigid plates positioned over the dorsal aspect of the distal phalanges, serving primarily to protect the fingertip from trauma and provide leverage for activities such as scratching or prying. The nail structure comprises the nail plate, produced by the underlying nail matrix (a germinal at the proximal nail fold), the nail bed (a specialized beneath the plate), and the (a thickened epidermal seal under the distal free edge that prevents entry and maintains subungual space integrity). Nail plate growth originates from mitotic activity in the matrix, advancing distally at an average rate of 3 mm per month, with variations influenced by age, health, and seasonal factors. Sensory capabilities of the fingertip arise from a high of specialized mechanoreceptors embedded in the glabrous , enabling acute tactile essential for manipulation and . Meissner corpuscles, located in the dermal papillae of the papillary , function as rapidly adapting receptors for detecting light touch and low-frequency vibrations (20-50 Hz). Pacinian corpuscles, situated deeper in the and , rapidly adapt to high-frequency vibrations (200-300 Hz) and changes, contributing to the perception of texture and slip. Merkel cell-neurite complexes, found at the epidermal-dermal junction, serve as slowly adapting receptors for sustained and fine spatial details, supporting and form recognition. These receptors collectively facilitate superior at the fingertips, with a threshold of approximately 2 mm, far finer than on other body regions, underscoring the fingers' role in high-resolution somatosensation.

Special Physiological Phenomena

Wrinkling in Water

When fingertips are immersed in , the skin typically develops a wrinkled or "pruney" appearance within 5 to 30 minutes, a response known as water-immersion skin wrinkling. This phenomenon results from of the digital arteries in the pulp of the fingers, leading to buckling of the overlying rather than osmotic swelling of the skin layers. The process is actively mediated by the , which triggers contraction of blood vessels and structural changes in the skin, distinguishing it from passive absorption. Evidence for this neural control comes from observations that wrinkling does not occur in denervated fingers, where sympathetic innervation is disrupted, such as in cases of peripheral damage. Similarly, interventions that block sympathetic activity prevent the wrinkling response by inhibiting signals to the vessels. This effect is confined to glabrous (hairless) on the and toes, with no wrinkling observed on hairy areas, highlighting the role of specialized epidermal structures in these regions. An evolutionary posits that this wrinkling enhances grip on wet surfaces, analogous to treads channeling for better traction, though this remains debated, with some studies finding no significant improvement in grip. Experimental studies support this, demonstrating that wrinkled fingers allow for more efficient handling of wet objects, such as tubes, by reducing slippage and required grip force compared to smooth .

Regrowth Capabilities

Human fingertips exhibit limited regenerative capabilities compared to other mammals and amphibians, with successful regrowth primarily observed in young children following distal . In children under 10 to 12 years of age, partial regeneration of the fingertip can occur after amputation distal to the nail bed, involving the formation of a blastema-like structure composed of proliferative mesenchymal cells that differentiate into soft tissues such as and pulp. This process has been documented in clinical studies, where conservative management without surgical intervention led to functional and cosmetic restoration in a of cases, particularly when the injury level allows for the preservation of the nail organ. The mechanism underlying this regeneration relies on epithelial-mesenchymal interactions, where the wound epidermis forms a signaling center that recruits and dedifferentiates local mesenchymal cells into a transient , a feature evolutionarily conserved from limb regeneration but significantly suppressed in mammals. In humans, this results in the regrowth of soft tissues covering the existing , restoring contour and sensation but not extending skeletal elements. Optimal outcomes require specific conditions, including no exposure of bone to prevent excessive scarring and the use of semi-occlusive dressings to maintain a moist environment that promotes epithelial migration and inhibits , even in non-sterile settings. Pioneering observations by Illingworth in a cohort of children highlighted these factors, showing high success rates for untreated distal injuries in promoting blastema-like healing. In adults, regenerative potential is markedly diminished, typically resulting in fibrotic scarring rather than true tissue replacement due to age-related decline in progenitor cell activity and inflammatory responses that favor fibrosis over blastema formation. Unlike in salamanders, where a robust blastema enables complete limb regrowth through patterned proliferation and differentiation, human fingertip regeneration does not achieve full digit replacement and is confined to the distal soft tissues, underscoring the evolutionary trade-off in mammalian healing priorities.

Neural Representation

The neural representation of fingers in the human brain is characterized by a somatotopic organization in the primary somatosensory cortex (S1), located in the postcentral gyrus of the parietal lobe, where the fingers occupy a disproportionately large area compared to their physical size. This mapping, first delineated through electrical stimulation studies, forms part of the sensory homunculus, with the thumb and index finger receiving the largest cortical representations to support their critical roles in tactile discrimination and manipulation. Functional neuroimaging confirms the extensive representation of the hand and fingers in S1, enabling high-resolution processing of touch and proprioception. Motor control of fingers is similarly mapped in the (M1) within the , adjacent to the sensory hand area, forming a motor that emphasizes fine, fractionated movements such as individual finger flexion and opposition. This organization facilitates precision grips, with overlapping representations allowing integrated sensorimotor coordination for dexterous tasks like pinching or typing. The cortical maps for fingers exhibit significant plasticity, as demonstrated in cases of where the deafferented finger areas in S1 can be invaded by adjacent representations, leading to sensations such as tingling in missing fingers triggered by touch to the face. Studies using and functional MRI have shown rapid reorganization following hand injuries, underscoring the adult brain's capacity for adaptive remapping to maintain sensory-motor function. Sensory information from fingers ascends primarily via two pathways: the dorsal column-medial lemniscus tract, which relays fine touch, vibration, and through large myelinated fibers to the of the and then to S1; and the , which conveys pain and temperature via smaller fibers, decussating early in the before reaching similar thalamic targets. Descending motor signals for precise finger movements travel through the , originating in M1 and projecting directly to spinal motor neurons, with a high proportion of fibers dedicated to hand control to enable fractionated finger independence.

Clinical Aspects

Congenital Anomalies

Congenital anomalies of the fingers are developmental abnormalities present at birth that affect the formation, structure, or number of digits in the hand. These conditions arise during embryonic limb development. Congenital anomalies occur in approximately 2-4% of newborns, with anomalies (including those of the fingers) representing about 10% of all such cases, for an overall prevalence of roughly 0.2-0.3%. The causes are multifactorial, with 40-50% remaining idiopathic, while the rest stem from genetic or environmental exposures such as teratogens. Genetic factors often involve in (HOX) genes or related pathways that regulate limb patterning, with inheritance patterns typically autosomal dominant for isolated cases. Polydactyly, characterized by the presence of extra digits, is the most common finger anomaly, with a prevalence of 23.4 per 10,000 live births. It is classified into preaxial ( side), central, or postaxial ( side) types, and postaxial polydactyly shows higher prevalence in African American populations at 1 in 100-300 births compared to 1 in 1,500-3,000 in Caucasian populations. , involving fusion of two or more digits, occurs in approximately 1 in 2,000-3,000 live births and can be simple (soft tissue only) or complex (including bone fusion); it is often inherited in an autosomal dominant manner. , marked by abnormally short fingers due to underdeveloped phalanges, encompasses multiple subtypes (A-E) caused by mutations in genes such as GDF5 for type C or for type E, and is typically autosomal dominant with variable expressivity. , a of one or more fingers (most commonly the fifth), has a reported incidence of 1-19.5% in the general population, frequently bilateral and more common in males, often resulting from genetic factors or as part of syndromes. Environmental teratogens like can induce severe finger anomalies, including reduction defects or phocomelia-like malformations, by disrupting vascular and signaling pathways during early . The Oberg-Manske-Tonkin (OMT) , endorsed by the American Society for Surgery of the Hand, categorizes these anomalies into malformations (e.g., , ), deformations, dysplasias, and syndromes, providing a framework for diagnosis and management that supersedes earlier systems like Swanson's. Diagnosis of finger anomalies often begins with prenatal , which can detect abnormalities such as extra digits or fusions as early as the second trimester, enabling informed counseling on potential functional impacts. These conditions may impair , fine motor skills, and overall hand function, necessitating multidisciplinary evaluation postnatally for surgical correction if indicated.

Injuries, Trauma, and Diseases

Hand injuries, including those to the fingers, represent a significant portion of visits, accounting for up to 30% of all injury presentations in some settings. These injuries often result from trauma such as falls, activities, or occupational accidents, with lacerations, fractures, and amputations being among the most common types affecting the fingers. Common fractures include the , a break in the neck of the , typically caused by a direct blow to a closed , as seen in scenarios. Initial involves immobilization with a splint or cast, and closed reduction may be necessary if angulation exceeds 30 degrees to restore alignment and prevent deformity. Another specific injury is Jersey finger, an avulsion of the flexor digitorum profundus tendon from the distal phalanx, often occurring during forced extension of a flexed , such as in sports like football. Treatment requires surgical repair, either direct tendon reattachment or open reduction and if a bony fragment is present, ideally within weeks of injury to optimize outcomes. Lacerations to the fingers involve cuts through the skin and potentially deeper structures like tendons or , requiring thorough , , and suturing to minimize risk and promote . Amputations, particularly of the fingertip, are managed conservatively for clean, guillotine-style injuries with and soft dressings allowing secondary intention , while more complex cases may necessitate or surgery. Traumatic crush injuries to the fingers can lead to , a condition where increased pressure within the fascial compartments compromises blood flow, causing severe pain that worsens with passive finger extension. Prompt diagnosis through clinical signs like the "five Ps" (pain, paresthesia, pallor, paralysis, pulselessness) is critical, with emergent to release compartments and restore . , another form of trauma from extreme cold exposure, results in tissue freezing and subsequent , particularly in the digits, with initial treatment focused on rapid rewarming in (around 40°C) followed by thrombolytic in severe cases to prevent vascular . Among diseases affecting the fingers, involves progressive degeneration of joint cartilage, commonly impacting the distal interphalangeal joints and leading to pain, stiffness, and bony enlargements known as . Management includes nonsteroidal anti-inflammatory drugs, for range-of-motion exercises, and in advanced cases, joint fusion or replacement to alleviate pain and restore function. Rheumatoid arthritis frequently involves the fingers through chronic , causing synovial inflammation in the metacarpophalangeal and proximal interphalangeal joints, which can lead to deformities such as swan-neck or . Disease-modifying antirheumatic drugs like are the cornerstone of treatment to control inflammation, supplemented by splinting and to maintain hand function. Trigger finger, or stenosing tenosynovitis, occurs when the flexor thickens, restricting gliding and causing the finger to lock in a bent position during movement. Conservative treatments include splinting to rest the digit and injections into the to reduce inflammation, with percutaneous or open surgical release reserved for persistent cases. Infections such as involve bacterial invasion around the nail fold, resulting in redness, swelling, and formation, often from minor trauma or . Acute cases are treated with warm soaks, if abscessed, and oral antibiotics like cephalexin targeting common pathogens such as . Raynaud's phenomenon manifests as episodic in the finger arteries, triggered by cold or stress, leading to blanching, , and pain due to reduced blood flow. Lifestyle measures like avoiding cold exposure and vasodilators such as are primary treatments, with severe cases potentially requiring sympathectomy.

Evolutionary and Developmental Aspects

Embryology

The development of fingers in human embryos begins with the formation of upper limb buds around the fourth week of gestation, arising from the lateral body wall through the activation of mesenchymal cells in the somatic layer of the lateral plate mesoderm. These buds initially appear as paddle-like structures, with the upper limb buds emerging slightly before the lower ones. By the sixth week, digital rays—precursors to the individual fingers—become evident within the flattened hand paddle, marking the onset of digit patterning. Separation of these rays into distinct fingers occurs by the eighth week through programmed cell death, or apoptosis, in the interdigital zones, which sculpts the free digits from the webbed paddle. Key signaling pathways orchestrate this process. The Sonic hedgehog (SHH) gene, expressed in the zone of polarizing activity at the posterior margin of the limb bud, establishes anterior-posterior patterning, specifying digit identities along the thumb-to-little-finger axis. (FGF) signaling, primarily from the apical ectodermal ridge, drives proximal-distal outgrowth and maintains the undifferentiated progress zone of mesenchymal cells. , a family of transcription factors, contribute to proximo-distal segmentation and overall limb organization by regulating the timing and spatial expression of developmental programs. Disruptions in these mechanisms can lead to congenital anomalies. For instance, , or webbed fingers, arises from failure of in the interdigital , often due to impaired BMP signaling or genetic mutations affecting cell death pathways. Amniotic band syndrome, resulting from early rupture of the and formation of fibrous strands, can cause constrictions leading to in utero amputations of fingers or other digits. By the twelfth week, finger differentiation is largely complete, including joint cavitation, ligament formation, and muscle differentiation, though mutations in genes like or GLI3 can underlie various congenital defects by altering patterning signals. These pathways reflect evolutionarily conserved mechanisms in limb development.

Evolution

The evolution of fingers traces back to the Devonian period, approximately 375 million years ago, when early tetrapodomorph fishes began transitioning from aquatic fins to limb-like structures capable of supporting weight on substrates. Fossil evidence from Tiktaalik roseae, a transitional form between fish and tetrapods, reveals robust fin rays and underlying endoskeletal elements that resemble primitive digits, suggesting these structures facilitated pushing against shallow-water bottoms and foreshadowed terrestrial locomotion. This innovation predated full terrestriality, with digits likely evolving first in aquatic environments to enhance maneuverability before the complete invasion of land. Recent research as of 2025 has shown that the genetic regulatory elements for digit formation were co-opted from an ancestral cloacal program in fish, illustrating how pre-existing developmental modules were repurposed in the evolution of limbs. A pivotal advancement occurred in early tetrapods like (up to eight digits on the forelimbs) and (seven on the hindlimbs), dating to around 365 million years ago, which possessed polydactyl limbs. These multi-digited appendages, preserved in Upper fossils from , indicate an initial phase of evolutionary experimentation, where excess digits may have provided stability and sensory feedback during the shift to land, aiding in weight distribution and grip on uneven surfaces. By the period, around 350 million years ago, the pentadactyl (five-digited) pattern emerged as a stabilized in basal tetrapods, such as Pederpes, marking a key event in limb evolution that balanced efficiency for terrestrial movement. Subsequent diversification unfolded within synapsids, the mammalian lineage originating in the late , where carpal bone homologies and increasing joint flexibility transformed pentadactyl hands into more versatile structures adapted for manipulation and locomotion. This progression, evident in fossils from non-mammalian synapsids like pelycosaurs and therapsids, culminated in the mammalian hand's enhanced dexterity by the era. In , which diverged around 60 million years ago, the development of opposable thumbs further refined this adaptability, enabling precise grasping of arboreal supports and later tool use, as seen in early euprimates. Conversely, in cetaceans, fingers underwent reduction and fusion during their return to aquatic life starting about 50 million years ago; forelimbs evolved into streamlined flippers with hyperphalangy—extra phalanges encased in —while hindlimbs were entirely lost, prioritizing hydrodynamic efficiency over individual digit mobility. Fingers played a crucial role in terrestrialization by providing structural support for load-bearing and propulsion, as inferred from the robust, digit-bearing limbs of tetrapods that allowed early ventures onto land. In hominids, this foundation enabled the evolution of precision grips for tool manipulation, with fossil evidence from species like around 3 million years ago showing hand proportions suited to use, driving further refinements in dexterity and expansion.

History and Terminology

Etymology

The English word "finger" derives from Old English , which traces back to Proto-Germanic *fingraz, ultimately originating from the *penkʷe, meaning "five." This linguistic evolution underscores the term's connection to the five digits typically associated with the human hand, excluding or including the thumb depending on contextual usage in early languages. Related anatomical terms share similar roots emphasizing the finger's role as a pointer or counter. The word "digit," often used interchangeably with "finger" in medical contexts, comes from Latin digitus, denoting "finger" or "toe," and later extended to numerical units (0-9) due to the ancient practice of counting on fingers. In anatomical nomenclature, "dactyl" or "dactylus" originates from Ancient Greek dáktylos, meaning "finger," and is applied to digits or phalanges, reflecting the structure's resemblance to jointed finger bones. Cognates appear across , such as German Finger and Dutch vinger, both stemming from the same Proto-Indo-European *penkʷe root, highlighting a shared cultural emphasis on the hand's fivefold . This numerological link manifests in ancient practices, where fingers facilitated counting systems; for example, many early civilizations, including those in and , used finger-based tallying that influenced decimal notations. The term's usage has evolved from such prehistoric and ancient depictions—evident in where finger symbols served as determinatives for manual actions and abbreviated large quantities like 10,000—to standardized modern terminology in and .

Historical Perspectives

In , (c. 460–370 BCE) described the characteristics of the arterial pulse, often palpated at the near the fingers, in association with conditions such as fever and , marking an early systematic observation of finger-related vascular dynamics. Building on this foundation, the Roman physician (c. 129–c. 216 CE) advanced anatomical understanding in the by detailing the muscular control of the hand and fingers through his dissections and experiments, which demonstrated how from the govern muscle movements in the digits, as outlined in works like Anatomical Procedures. Galen's descriptions emphasized the intricate interplay of tendons and muscles enabling precise finger actions, influencing medical thought for over a millennium. During the , revolutionized anatomical study with his 1543 publication De Humani Corporis Fabrica Libri Septem, which included detailed illustrations and dissections of the hand's phalanges, correcting Galenic errors and providing the first accurate visual representations of bone structure based on human cadavers. Vesalius's work shifted toward empirical observation, depicting the three phalanges per and their articulations with unprecedented precision, laying groundwork for subsequent hand . The late 19th century brought transformative imaging capabilities with Wilhelm Conrad Röntgen's discovery of X-rays on November 8, 1895; the first image revealing the internal bony structure of the fingers was a radiograph of his wife's hand, adorned with a ring, taken on , 1895, enabling non-invasive visualization of phalanges and joints. In the 20th century, microsurgery emerged as a milestone, with the first successful digital (a ) achieved in 1965 by Shigeo Komatsu and Susumu Tamai in , utilizing operating microscopes and vascular to restore amputated digits, fundamentally advancing reconstructive techniques. Fingers have held significant cultural roles across societies, such as in ancient where one-handed systems—using thumb-to-finger folds for numbers 6 through 10—facilitated communication and arithmetic, a practice rooted in historical numeral traditions dating back over two millennia. Similarly, prohibitions on pointing with the appear in various cultures, including Japanese and some Indigenous American societies, where it is viewed as aggressive or disrespectful, often replaced by open-palm gestures to indicate direction or reference. Pre-modern anatomical knowledge exhibited notable gaps, particularly in understanding regeneration, which was largely unrecognized beyond anecdotal observations of limited fingertip regrowth in children, without comprehension of underlying cellular mechanisms. Neural mapping of fingers, involving somatotopic organization in the , remained entirely unexplored until 20th-century neurophysiological studies, leaving ancient and medieval scholars without insight into sensory-motor representations.

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