A backstop for your fingertip
What Are Fingernails For?
A nail is a hard plate that lets the soft pad underneath push back, which is what makes a fingertip so sensitive.
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Step 1 of 5
A nail is made of the same stuff as hair.
Cells at a hidden root fill themselves with keratin and die, packed far more tightly than in a hair, forming a flat plate instead of a strand.
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Step 2 of 5
The plate is what makes your fingertip work.
Squeeze something and the soft pad would just squash away. The nail stops it spreading backwards, so the pad presses firmly against whatever you are holding.
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Step 3 of 5
That backstop is what fine touch needs.
Sensors in the pad only report when they are compressed. Without something rigid behind them, small pressures would be absorbed and never felt.
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Step 4 of 5
It grows from a hidden root, not the white crescent.
New nail is made under the skin behind the cuticle. The pale half-moon is simply the part of that root you can see through the plate.
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Step 5 of 5
Damage the root and the nail is changed for good.
The plate itself cannot repair — it is dead. A ridge or a split grows out over months, but a permanently injured root makes a permanently odd nail.
Fingernails grow about 3 mm a month; toenails manage roughly a third of that. A fingernail takes about six months to replace itself entirely.
The short version
A fingernail is a hard backstop that stops your fingertip pad from squashing away, which is what makes gripping and fine touch possible.
Try it yourself
Press a fingertip on the table, then press the same spot on the pad of your palm. The nail is why one feels precise and the other vague.
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