 Fingernails and toenails grow from a point near the
roots below the skin, at the base of the nail where the nail
is very thin. White in color, and half-moon in shape, this
semi-circle is appropriately named the "lunula, " and
comprises a group of cells that manufacture keratin, a
dead, hoof-like protein. The keratin like protein produced,
gathers and merges with the nail plate, the dead armor that
protects the soft and tender nail bed underneath, and pushes
the entire nail up and out. Though the fingernails and
toenails grow an average of two inches per year, their growth
slows with age, and the average adult's fingernails grow only
one inch over the course of eight months.
The base of the fingernails and toenails, as well as some
of the nail along both sides of the nail, are embedded into
the skin. Unlike other skin, this skin contains elastic fibers
that connect it to the fingernail or toenail, and hold it
firmly in place. The cuticle , a rim of skin over the
lunula, protects it from bacterial infection, serves as a
shock absorber, and shields the nail from any sudden
impacts.
Though many consider dressing the fingernails up to go out
a statement of beauty, or one of vanity, they serve those in
the medical field as a diagnostic tool. Normally, the lunula,
or half-moon, is white in color, indicating proper nutrition
and good overall health. Blue lunula raise red flags that
circulatory problems to the fingers may exist. Nails that are
hard, brittle, and tend to split easily, may also be
clues to poor circulation, infection, or disturbances of the
glandularand nutritional systems.
Further nails that curl sharply around the finger point
to coronary , liver, or lung diseases. Nails that are
sunken in appearance often indicate anemia, a condition
where an insufficient amount of oxygen is carried by the
blood.
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指甲下端的白色弧影，甲弧影
角蛋白，角質(zhì)
角質(zhì)層
硬而脆的
腺的
冠狀動脈
貧血癥
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