Lunula (anatomy)
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The lunula, or lunulae (pl.) (nail moon), is the crescent-shaped whitish area of the bed of a fingernail or toenail. The lunula is the visible part of the nail matrix (i.e. the root of the nail).
It appears by week 14 of gestation, and has a primary structural role in defining the free edge of the distal nail plate (the part of the nail that actually grows outward).
Appearance
It is located at the end of the nail that is closest to the skin of the finger but still lies under the nail. It is not actually white but only appears so when seen through the nail.
It is half-moon-shaped, and has unique histologic features.
The lunula is most noticeable on the thumb, and not everyone's lunula is visible.
Clinical significance
The lunula and the nail itself are good places to find warning signs of certain diseases such as liver disease, kidney disease, heart problems, and lung diseases.[1][citation needed] Any colour differences or unusual lines may indicate some type of disease or insufficiency. However, vertical lines on one's fingernails are normal as one ages.
Lunular anomalies include changes in form, structure or colour. Lunular dysmorphologic features (that is, anomalies in form) can be characterized by macrolunula, microlunula or anolunula, and nonconvex lunula. Lunular dyschromias (colour anomalies) can be confluent or spotted or can be characterized by longitudinal coloured bands that traverse the lunula. Alterations in the morphologic features or colour (or both) of the lunula can be an indication of either a cutaneous or a systemic disorder. A deep red lunula and pale nails is associated with congestive heart failure.
REFERENCES
[1] ROBERT S. FAWCETT, M.D., M.S., SEAN LINFORD, M.D., and DANIEL L. STULBERG, M.D. Nail Abnormalities: Clues to Systemic Disease [Cover Article]. American Family Physician www.aafp.org/afp VOLUME 69, NUMBER 6 MARCH 15, 2004 Pp. 1417-1424.
See also
- ^ Nail Abnormalities: Clues to Systemic Disease http://www.aafp.org/afp/20040315/1417.html