Hair

The hair is a thread-like production of the skin, covering partially or completely the skin of the Mammifère S. When the cover of the skin is complete, one speaks about peeling in the animals in general. Pilosity relating to the top of the head is called the hair at the human being, that concerning the chin is the Barbe at the man, finally that of the chin and of the neck the Crinière in the animals is called. Under the arms and around the genitals the hairs seem to have functions badly included/understood, respectively of evaporation of the Transpiration, and perhaps of diffusion of Hormone S. The hairs, hair and others Phanère S could also contribute to the detoxication of the organization, one finds there, for example, part of poisons such as lead, mercury or the arsenic absorptive via the food or the breathing which accumulate there. In the ears and the nose, hairs play the part of filter and alarm in the event of penetration (insect, object.)

An animation in 3D on the hair and its physiology is visible in the medical encyclopedia Vulgaris:

The hair, also called Follicule pilous or pilar stem is enraciné to approximately 4 mm under the skin (derm). The base of the hair is named " bulb pilaire". This one consists of Kératinocyte S and Mélanocyte S which multiplies very quickly by successive Mitose S.

The kératinocytes harden to constitute the pilar stem then die. The pilar bulb contains a mélanocyte for about thirty kératinocytes. The mélanocytes transmit the Mélanine to the kératinocytes: the pilar stem thus pushes pigmented until the disappearance of the mélanocytes with the age.

Anecdotes

Why the hairs roughcast are when one is afraid?
Face with certain scenes or certain noises, the information transmitted to the brain causes an emotion which starts measurements of Autoprotection. The swelling of the hairs would be a Réminiscence our origins Préhistoriques. This Reflex, running in the animals, is used to impress the enemy while appearing larger. The goose flesh causes the same phenomenon, in cold reaction by the constriction of the smooth muscles, under the skin.

It is a small smooth muscle, called muscle arrector (or horripilator) which makes it possible the hair to be drawn up. It reacts cold, or with other stimuli.

In certain countries, the hair is or was object of Censure (with the Japan it is the vision of pilosity more than of nudity which was prohibited with the cinema or in the cartoons).

In the animal

Many invertebrates (of which insects) and vertebrate have hairs whose functions seem very diverse (peeling with hollow hairs protective with sensor of heat and radiation UV in the polar bear, with the hairs of moustache of the cat or Vibrisse of the bald person mouse which plays a part for balance, the food and perception.
Presque all the insects are abundantly furnished with microscopic hairs whose functions are badly known.

The hairs are used by the naturalists to identify animals.
on can even ajourd' today shoot some from genetic information at the individual or the population of which it forms part, in particular for the follow-up of animals become rare or difficult to observe (wolf, bear)

At the plants?

The equivalent of the hairs exist at many plants, with roles badly included/understood, sometimes protective and possibly transformed into spines or darts (ex: Nettle). In certain cases the hairs seem to play a big role of sensor of particles or water sensors by nucléant the Rosée by “effect of point”

See too

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