What is a nail?
A: A nail is a claw-like plate at the tip of the fingers and toes in most
primates.
Nails correspond to what found in other
animals?
A: Claws.
Fingernails and toenails are made of what?
A: A tough protective protein called alpha-keratin, which is a polymer.
Where else is alpha-keratin found?
A: In the hooves, claws and horns of vertebrates.
The nail plate is the visible hard nail area from the
nail root to the free edge, made of what?
A: Translucent keratin protein.
Several layers of dead, compacted cells cause the nail
to be what?
A: Strong but flexible.
Its (transverse) shape is determined by what?
A: By the form of the underlying bone.
The nail plate is strongly attached to what?
A: The nail bed and does not contain any nerves or blood vessels.
A healthy fingernail has what function?
A: Protecting the distal phalanx, the fingertip, and the surrounding soft
tissues from injuries.
It also serves to enhance precise delicate movements of
the distal digits through counter-pressure exerted on what?
A: The pulp of the finger.
The nail then acts as a counterforce when the end of
the finger touches an object, thereby enhancing what?
A: The sensitivity of the fingertip, although the nail itself has no nerve
endings.
Finally, the nail functions as a tool enabling what?
A: An extended precision grip for pulling out a splinter in one's finger.
In mammals, the growth rate of nails is related to
what?
A: The length of the terminal phalanges (outermost finger bones).
Thus, in humans, the nail of the index finger grows faster than that of the little finger; and fingernails grow up to four times faster than toenails.
In humans, fingernails grow at what rate?
A: An average rate of approx. 3.5 mm (0.14 in) a month.
In comparison, how fast do toenails grow?
A: About half as quickly (approx. average 1.6 mm (0.063 in) a month).
Fingernails require three to six months to regrow
completely, and toenails require how long?
Actual growth rate is dependent upon what?
A: Age, sex, season,
exercise level, diet, and hereditary factors.
Contrary to popular belief, nails do not continue to
grow after what?
A: After death; the skin dehydrates and tightens, making the nails (and
hair) appear to grow.
The nail is much more permeable than what?
A: The skin, and the composition of the nail includes 7–12% water.
This permeability has implications for penetration by
what?
A: Harmful and medicinal substances, and cosmetics applied to the nails can
pose a risk.
Water can penetrate the nail as can many other
substances including what?
A: Paraquat, a fast-acting herbicide that is harmful to humans.
What is the best way to care for nails?
A: Trim them regularly.
Filing is also recommended, as to keep nails from
becoming what?
A: Too rough and to remove any small bumps or ridges that may cause the nail
to get tangled up in materials such as cloth.
