fingernail growth

[bunny29]

How exactly do fingernails grow? I know they grow from the base, so do they attach and detach as they move up the finger?

[demitry-hed]

Nails grow at an average rate of 0.1 mm/day (1 cm every 100 days) [1]. Fingernails require 4 to 6 months to regrow completely. Toenails require 12 to 18 months. Actual growth rate is dependent upon age, season, exercise level, and hereditary factors.

This growth record can show the history of recent health and physiological imbalances, and has been used as a diagnostic tool since ancient times.[2] Major illness will cause a deep horizontal groove to form in the nails. Miscoloration, thinning, thickening, brittleness, splitting, grooves, Mee's lines, small white spots, receded lunula, clubbing (convex), flatness, spooning(concave) can indicate illness in other areas of the body, nutrient deficiencies, drug reaction or poisoning, or merely local injury. Nails can also become thickened (onychogryphosis), loosened (onycholysis), infected with fungus (onychomycosis) or degenerative (onychodystrophy); for further information see nail diseases.

[bunny29]

Thank you for trying, but that doesn't answer my Q.

[kwicky]

At a guess I would say exactly the same as hair grows. If you dye your hair the growth is from the roots forcing the dyed hair outwards.

[bunny29]

But it's attached all the way along its length, unlike hair, so how does it move along?

[theprof]

Nails grow by division of a matrix of cells in a germinative layer behind the exposed nail and under the skin. This is the nail root.

The cells in the matrix layer multiply and the older cells move forward and eventually become exposed as the nail tissue we are familiar with. By this time, the cells will have keratinised. This part of the nail is known as the body or nail plate.

The nail plate slides in a forward direction over the nail bed due to the growth of the cells at the rear of the nail bed � in effect it�s being pushed forward from the matrix. However, it remains attached to the nail bed throughout its journey because the nail plate takes the nail bed forward with it. The reason this is necessary is because the nail plate requires nutrients in order to survive and the minute blood vessels in the nail bed also supply the nail plate.

Now because the nail plate extends further than the nail bed at the tip of the nail, contact between the nail plate and nail bed is broken. The supply of nutrients to the nail plate also stops. Once this occurs, the cells in the area die and turn white.

This whiteness may also be seen at the lunula, which is the semi-circular area at the base of some nails. Lunulae, where present, are not attached to the nail bed.

Interestingly, most people are without lunulae on their little fingers, whilst the lunulae are always prominent on the thumbs; the rest of the fingers vary in-between.

Nails are not attached along their length as I showed earlier. Therefore they do not attach and detach as they move up the finger. They just glide along taking the nailbed with them.

(continued)

[theprof]

If you speak to someone who's had a toenail or fingernail removed ( I've had the dubious pleasure of having eight taken off my own toes over the last few years), they'll tell you that the state registered podiatrist or surgeon inserts a type of pliers beneath the nail and just yanks it forward and out - after a local nerve-block naturally!

Although the nail bed bleeds, it's not profuse bleeding as the nail was never attached to it proper.

[theprof]

I should have added that the bleeding that does occur during nail removal is from the base of the nail, where the extensive network of blood vessels are ruptured.

Apologies if it sounds gory!

[bunny29]

WOW, thank you theprof!!
That makes so much sense now.

[Hippy]

Wow! Clever Prof.

I dropped a piece of furniture on my big toe - ouch. It meant that the nail became loose and during a bath I fiddled with it and yanked it off. No pain there. A bit of blood as you say from the base area.

This was my big toe. The skin on top hardened and the nail grew back within three months. I thought that was really fast. I'm sure it's slowed down since. I also have the bonus that previously it was ingrowing on one side, but no longer. it is much a better shape.

[theprof]

I'm glad I managed to clarify it for you bunny29. Nail anatomy and growth is one of those things that's sometimes difficult to get your head around.

Hippy, a professor I may be but I'm really not that clever at all. For example, ask me anything about sport and I wouldn't have a clue!

Seriously though, as you've confirmed, a nail will sometimes come out naturally with hardly any bleeding. If the nail is loose or damaged sufficiently and not attached to the matrix, there's no pain as there are no nerves linking the nail bed to the nail plate. The pain only arises when a nail is still attached to the matrix, hence the need for an injection of local anaesthetic on both sides of the toe (or finger).

Most of the time, it's better to be rid of a damaged nail and allow a new one to grow from scratch as you've discovered yourself.