Finger

Evolution and Anatomy of Fingers

• Land vertebrate fingers
• Fingers of tree frogs, red-eyed crocodile skinks, red squirrels, and bats
• Terrestrial vertebrates' forelimbs evolved from lobe-finned fish
• Variation in the basic pentadactyl plan and the metacarpals and phalanges
• Different fingers of terrestrial vertebrates are homologous
• Primates, like chimpanzees, have specialized lower limbs for manipulation and fingers on their lower limbs
• Human fingers
• Humans typically have five digits on each hand
• Some people have more or fewer than five due to congenital disorders or amputations
• Definitions of finger vary, with some including the thumb and others not
• English dictionaries describe finger as one of the five digits or one of the four digits excluding the thumb
• Thumb can be called a finger, depending on the definition
• Anatomy
• Skeleton of the hand includes the thumb, palm, metacarpal bones, and phalanges
• Each finger has three joints: metacarpophalangeal, proximal interphalangeal, and distal interphalangeal
• Sesamoid bones provide extra leverage and reduce pressure
• Articulations include interphalangeal articulations and metacarpophalangeal joints
• Muscles in the palm and forearm control finger movements

Muscles and Movements of Fingers

• Muscles
• Each finger can flex, extend, abduct, adduct, and circumduct
• Flexion is the strongest movement, produced by large muscles and augmented by additional muscles
• Finger movements are not completely independent due to finger interdependence
• Finger joints are moved by muscles in the palm and forearm
• Muscles of the fingers can be divided into extrinsic and intrinsic muscles

Sensory Capabilities of Fingers

• Skin
• Fingertips have the highest concentration of touch and thermoreceptors
• Fingers are extremely sensitive to temperature, pressure, vibration, texture, and moisture
• Fingers can feel nano-scale wrinkles on seemingly smooth surfaces
• Fingers are commonly used as sensory probes to ascertain properties of objects
• Fingertip wrinkling in water is caused by blood vessel constriction in response to water exposure
• Anatomy and Function of Fingers
• Fingertips provide better handling of wet objects but no advantage for handling dry objects.
• A 2014 study failed to demonstrate any improvement in handling wet objects with wrinkled fingertips.
• Fingertips can regrow in less than 8 weeks if torn off, although they may not look the same as before.
• Healing does not occur if the tear happens below the nail.
• Distal phalanges are regenerative in youth, and stem cells in the nails create new tissue for fingertip regrowth.

Brain Representation and Clinical Significance of Fingers

• Brain Representation of Fingers
• Each finger has an orderly somatotopic representation in the cerebral cortex.
• The somatosensory cortex area 3b and part of area 1 are involved in finger representation.
• Supplementary motor area and primary motor area also have distributed, overlapping representations of fingers.
• In syndactyly, where fingers are fused, the cortical maps of individual fingers also form a club hand.
• Surgical division of fused fingers can separate the cortical maps and improve hand function.
• Clinical Significance of Fingers
• Anomalies such as polydactyly (extra fingers) and symbrachydactyly (underdeveloped fingers) can occur.
• Phalanges are commonly fractured, and damaged tendons can cause loss of fine motor control.
• Fingers can be affected by diseases like rheumatoid arthritis, gout, and neurovascular disorders.
• The ratio of lengths between index and ring fingers has been linked to various physical and behavioral traits.
• Fingers are used by diabetics for blood sugar testing, and they can be affected by conditions like Raynaud's phenomenon.

Cultural and Linguistic Aspects of Fingers

• Cultural and Linguistic Aspects of Fingers
• The name 'pinkie' derives from the Dutch word 'pinkje'.
• In some languages, the translated version of 'fingers' can refer to both hand and foot digits.
• English distinguishes between fingers and toes for foot digits.
• Finger snapping is a cultural gesture associated with making a sharp sound by pressing the fingers together and then releasing them.
• The term 'digit' is used in scientific and medical contexts to refer to both fingers and toes.

Finger Mentions

Finger Data Sources