Definition of Nails

Nails – The hardened epidermal layer covering the top surfaces of the tips of the fingers and toes. Nails are made of cornified, compacted skin cells (keratinocytes) that grow from the base of the nail (matrix or nail-bed root).

Though the cells of the matrix are alive, the cells that make up the nails are dead. New cell growth from the matrix pushes the nail outward across the tip of the finger or toe. In adults the fingernails grow about two tenths inch in a week. The cells the matrix produces today will reach the end of the finger in about six months.

Like the skin, the nails provide insights into the overall health situation of an individual. Certain changes in the nails signal specific health conditions. Such characteristics include

  • banding: stripes of dark or light across the width of the nail bed, visible through the nail
  • Beau’s lines: indentations in the nail surface that extend across the width of all the nails at about the same position on each
  • clubbing: end of the finger or toe becomes enlarged and the angle between the nail fold and the nail plate exceeds 180 degrees
  • discoloration: may be widespread throughout the nail or occur in spots or streaks
  • koilonychia: nails soften and the edges rise, leaving a large spoonlike indentation in the center of the nail
  • leukonychia: white spots or streaks in the nail
  • onycholysis: separation of the nail from the nail bed
  • petechiae: red or dark spots beneath the nail
  • stippling: the formation of small pits in the surface of the nail

Health Implications of Nail Characteristics

Nail CharacteristicPossible Health Implications
Beau’s linesserious injury or illness that disrupts nail growth
clubbingchronic pulmonary conditions, heart failure, low blood oxygen levels
dark band at tops of nails, bottoms of nails normal color (Terry’s nails)age, cancer, congestive heart failure, diabetes, cirrhosis, hyperthyroidism levels
koilonychiairon-deficiency anemia
leukonychiaarsenic poisoning, mineral deficiency, trauma to the nail matrix
onycholysisthyroid disease, fungal infectionpsoriasis, adverse drug reaction
petechiae (pinpoint hemorrhages)endocarditis, thrombocytopeniasystemic lupus erythematosus (SLE)
stipplingpsoriasis, alopecia areata, injury to the nail
white band at the bottoms of nails, tops of nails normal color (half-and-half nails)uremia, kidney failure
yellow nail syndrome (yellow-green discoloration consistent through all nails)chronic pulmonary disorders such as bronchitis and emphysema,nicotine staining

For further discussion of integumentary structure and function please see the overview section “The Integumentary System.”


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