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34

Hair actually does have a limit to its growth. All hair cycles between periods where it grows, and when a new stand appears, which pushes the older, long hair out. Hairs that are generally shorter, like eyebrows or arm hairs, have a shorter growth period before a new hair pushes the old one out. The hair on your head actually grows much faster than many ...


22

This is an interesting question, and there are a number hypotheses available to explain this phenomenon. The short answer (as far as I can say after my literature search) is that we don't know the answer for sure. The long version follows below. The main problem with all these hypotheses is that though they may have a valid point, a definitive hypothesis ...


20

Hair grows from the follicle; there is no way for the follicle to determine if the hair tip is trimmed or not. This is unlike plant shoot/root growth that happens at the tip. Also there is no signaling from tip to follicle. Hair growth has four stages: Anagen (Initiation), Catagen, Telogen (resting) and Exogen (falling off). Initially the primary follicle ...


15

The pigmentation of hairs is achieved by the follicular melanocytes (specialized pigment cells) at the base of the hair shaft. These cells produce the pigment which is subsequently transported into the cells which produce the hair and integrated into the hair matrix. Besides genetic reasons, there are two major ways of losing this pigmentation. First, as a ...


10

There's no harm in plucing a hair, but it won't do you much good Plucking the hair will indeed get rid of the hair - but only temporarily "The follicle (the little tube beneath the skin that produces the hair) is still alive and will produce another hair to replace the one that was pulled out So actually if you DON'T damage the follicle (which is ...


8

Hair color is not so simple as that. Most traits, especially those as complex as color, are controlled by many alleles at many loci. That's why there are different kinds of brown, blond, and red hair in the population. There is no "hair color gene." A fascinating paper came out a few years ago, identifying dozens of SNPs playing a role in hair and eye ...


8

A search of the Internet shows many anecdotal cases of people reporting their grey or white hair returning to their normal color.  Interestingly, many of these ancedotal cases begin by stating that their hair had turned grey or white at a young age (early 20s) before returning to it's natural color.  Finding a scientific explanation does not seem as easy. ...


8

Hair colour is maintained by a pigment called Melanin which also affects skin colour too. When the melanin content in your hair decreases, it turns grey and eventually white. Multiple factors affect melanin levels in your body. 1) age 2) Genetics 3) Diseases 4) Cell Stress You can read about them in a little more detail here. I cannot specifically ...


8

Nice question. I must say it took me many hours to get satisfactory answer. Hairs are made of keratin molecules, which contain cysteine. Cysteine has thiol (-SH) group, by which it can form disulfide (-S-S-) bond with another cysteine of another keratin, causing bending of hair. See this image from here: Curling of hair can be justified on both microscopic ...


7

It can actually be for both reasons and it more or less depends on the age what happens. The pigment of the hair is produced by pigment cells (the melanocytes) in the hair bulge and is then integrated into the growing hair (image from here). The pigment melanin produced by these cells can be destroyed by reactive oxigen species which then leads to grey hair ...


7

Since it's been so long, I guess a rushed speculative answer might be at least an idea. DNA gets damaged randomly all the time, and repair mechanisms are in place to fix it. When the damage is too large or of a very complex kind, permanent mutations can develop, and cause disorders such as cells proliferating without control - i.e. tumours. I could imagine ...


7

Think of what happens when you don't wash your hair for days. It gets oily and greasy. This oil-like substance on your hair is called sebum and mainly works as a lubricant . The Sebaceous glands responsible for excreting sebum don't stop working when the hair follicles attached to them do. The result is a "shiny" head.


6

From a little research I have been able to find some of the hypotheses and speculations but no papers expressly confirming or denying the matter. One theory displayed in "The evolution of mammalian keratinized structures" (abstract only) is that mammalian hair developed along the following pathway: Hair follicles develop between reptilian like scales. A ...


6

Hair does not grow back thicker when it is cut. This is somewhat of an optical illusion because when you shave with a razor it leaves the top of the hair flat rather than pointed so it appears thicker. For instance see this picture: As you can see the hair is tapered at the top and when cut loses this taper to leave a large cross-sectional area. I would say ...


5

We shampoo our hair because of sebum. In humans, sebaceous glands are are most numerous on the face and scalp, with (on the scalp at least) several glands plus a hair follicle making up a pilosebaceous unit. Each gland secretes sebum, initially a colorless and odorless fatty substance (plus dead cells) that spreads from the scalp outward over the hair, but ...


5

As to the early evolution of mammalian hair, Rowe et al. (2011) hypothesized that the primitive function for hair was not thermoregulatory, but rather for tactile sensation (contra the hypotheses of Spearman and Maderson). Rowe et al. say: Body hair develops as migrating neural crest cells induce patterns of tiny placodes that mature into hair follicles ...


5

The molecular basis of copper-transport diseases in Trends in Molecular Medicine, Volume 7, Issue 2, 1 February 2001, Pages 64–69, has a link to a 1973 paper by JM Gillespie entitled "Keratin Structure and Changes with Copper Deficiency," stating Menkes patients are often diagnosed from their unusual hair structure – termed pili torti – also known as ...


4

Interesting question, I am not sure if I have a definite answer, but at least some ideas: The pigment in the hair is made by specialized cells, the melanocytes. The make the pigment (eumelanin=dark and pheomelanin=red/yellowish) which is then deposited into the growing hair. They are located at the bottom of hair bulb and usually die at the end of each hair ...


4

As a general rule, you might want to check wikipedia before posting here. On the other hand, I am glad you made me look the answer up. Goose-bumps warm you up a little. "During the formation of goose bumps, the body is warmed from the muscle tension in piloerection." There are other reasons, which do not directly serve humans, but may be a remnant ...


4

I've been trying to figure out something that works for some time. I have recently tried 3 cheap protocols using commonly available lab reagents. I was using buccal samples (0.2 ml of spit). 1) Boil the sample in Tris EDTA Buffer 2) NaOH Extraction 3) Direct N Lyse I compared them to a genomic DNA extraction kit (FAST DNA Prep - MP Biomedicals). I ...


3

Hairs (with their nerve rich follicles) are sense organs, extending our sense of touch beyond the skin. When things disturb our hairs we feel them; bugs, breezes, close encounters. During fright or arousal goosebumps cause the hairs to stand on end, extending our sense of touch to it's furthest distance. In the process the hair shafts that are otherwise laid ...


3

There are a few different types of hair on a cat. But I think you are referring to the down hair on the cat. It will also vary on the breed of domestic cat. As a general statement, you can find a lot of quirky characteristics of mammals by looking at early genetics papers where people where trying to find genetic elements to obvious phenotypes. For the ...


3

I think it's best to break this question up in to two parts: What mutations account for red hair and fair skin in humans How might these same mutations affect pain sensation MC1R variants & red hair The MC1R gene encodes a transmembrane receptor protein (belonging to a very common family of receptors), called melanocortin 1 receptor. It also has ...


3

In order to keep the hair from decomposing, my first assumption is you'd need it in an environment that inhibits decomposers, e.g. dry. We can see in the mummification process that hair may be preserved for hundreds of years. Hair is also composed largely of keratin, however, and in my own search of the literature: (1) we need microbial (bacteria, fungi) ...


3

The motion of the comb against your hair remove electrons from the hair and deposits them on the comb. The positively charged hair and negatively charge comb now attract each other due to their opposite charges. You can read about this is any introductory Physics text, the topic is "static electricity". I doubt any harm is done to your hair, the issue is ...


3

All people don't have those hair colors. All people from those Northern countries aren't blond, and there are blond people outside of Northern Europe; I don't know if you count Melanesians as "Asian", but they have blond people among them: https://en.wikipedia.org/wiki/Melanesians#Incidence_of_blond_hair_in_Melanesia Still; there are two, really three, ...


3

Those are just ordinary hairs growing in your ear, like the kind you find in your nose and, if you are fortunate, on the top of your head. The "hair cells" of the inner ear aren't really "hairs" at all, they are totally different, and you would never find them falling out of your ear. Hairs like on your head are protein filaments produced by follicles in ...


2

In hair and nail growth new cells are added to the bottom. These cells are produced at the follicle. There are three stages called: Anagen : active growth Catagen : end of active growth Telogen : total stop of follicular growth I don't know what you mean by like grass but both nails and hair have a first in first out order. Feathers present a contrasting ...


2

Our body contains a lot of salt and which act as electroyte,so when we comes in contact of electric source then the electrolyte helps in the conduction of electric current through out body,


2

Our own hair will also turn gray (indeed, yours seems to be on its way, if you don't mind me saying so) but there need not be an advantage to that; if it doesn't affect our ability to have successful children it probably doesn't matter much to evolution or selection. When it comes to animals that interact with humans, though, many traits are selected for, ...


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