Why do fingernails keep growing? So that we always have them. If they didn’t keep growing, they would get worn down and be of no use.
How do nails grow? Nails are made of keratin, which is the same substance our hair is made of. Keratin is a fibrous protein that is very tough and insoluble in water. It goes into our nails and hair, but also scales, feathers, horns, claws, and hooves of animals. You might not think it when you look at your nails, but they start out life as living cells. The nail root grows out of a matrix of cells in the finger, and it is connected to nerves and blood vessels. The matrix produces nail cells, which push the older nail cells in front of them as they grow. The white part at the bottom of your fingernail that you can see is the top of the matrix where the new nail cells are created. The older nail cells get pushed further up the nail and they harden as they go. The older nail cells compress and become translucent as they harden. Their translucency is the reason why they are pink: we can see the blood vessels in our fingers through them. The nail is attached to the nail bed all the way until it exits the sterile barrier at the top of the fingernail, and this is the part that we would trim away if they get too long. Once the nail crosses the sterile barrier, there is no more blood supply and the nail cells die. Nails grow fairly slowly. Fingernails grow at a rate of about 3.5 mm a month and toenails grow at about 1.6 mm a month.
Why do we need fingernails? They do 6 main jobs for us. Firstly, they protect our fingers. We have very sensitive fingers that a packed full of nerves. We need that to be able to feel and sense the world around us. The nail keeps all these nerves safe and away from harm.
The nails support our fingers. Many animals have claws, but if an animal is trying to rapidly climb from tree to tree, nails can get in the way. Our fingers are quite wide, which gives us a large surface area to grip things, such as tree branches or tools. The wide nail we have on each finger creates a hard layer of support that wouldn’t come from the finger bone alone. It allows us to have wider fingers than we otherwise could, giving us far more grip.
The nails help us to sense and touch. The nail itself might be hard, but there are many nerves under the nail. When we touch something, the pressure of the nail on the back of the finger can tell us how hard we are touching something. It gives the fingers something to push against.
Nails help us fight. In the same way that many wild animals have claws for fighting, our nails can be pretty dangerous. Anyone who has accidentally scraped their hand with one of their own nails can attest to this.
Nails help us grip. We grip more with our fingers than our nails, but we can dig the nails in, if we need to. And they can help us grip small things that would be too small for our fingers alone.
Nails help us to find food. Our nails are very good at helping us dig through soil and roots to find food.
Fingernails have a whole host of uses, but toenails are probably primarily for protection. Many primates can grip branches with their feet and in these cases, the nail would serve much the same purpose as fingernails, but for humans, when we started to walk upright, their purpose became largely protection of the toes.
So, why do fingernails keep growing? Because we need to be able to grow out any damage that might occur. When we lived in the wild, we used nails for so many things that they could very easily be broken or damaged. If nails were made out of a harder substance, such as enamel, that didn’t grow, we would be stuck with any damage to the nail forever. With fingernails that grow, the damage will grow out in a few months and the nail will be as good as new. And this is what I learned today.
Sources
https://www.livescience.com/65277-why-fingernails-keep-growing.html
https://en.wikipedia.org/wiki/Keratin
https://en.wikipedia.org/wiki/Nail_(anatomy)
https://www.nytimes.com/2015/08/25/science/the-inexorable-forces-of-nail-growth.html
https://www.verywellhealth.com/nail-anatomy-growth-structure-and-more-1068848
https://patient.info/news-and-features/why-do-humans-have-nails