GROWING IS COMMUNICATION

Communication is certainly a very fashionable word, but it must be acknowledged that life, at least in the biological sense of the term, is above all a story of cellular communication. The life cycle of hair provides a remarkable illustration of this.


  Four phases in a cycle


Hair grows, falls, regrows and so on. Each hair life cycle is made up of 4 successive phases


The phenomenon is extraordinary and unique in the human body because it is by absolutely the same process as occurs in the embryo that the hair follicle reforms and again penetrates the dermis : we call this neomorphogenesis .

So, in a completely independent cyclical way, each hair follicle, like a yoyo, goes down inside the dermis, then rises, then redescends, then rises again ...

But this beautiful cyclic phenomenon can seize up and hair loss increase.

There is another astonishing thing to be considered. If in fact, for example, all our hairs were in the same phase at the same time, they would all move simultaneously into the telogen phase . In other words, they would all fall out in a short space of time before regrowing. We would undergo the phenomenon of moulting. However, this is obviously not what happens. Why not? The answer is very simple: each hair is autonomous. Yes, each one of our 100,000 or 150,000 hair follicles is absolutely independent from its neighbour!
Each hair leads its own life, some growing while others fall or regress. The fact that a normal head of hair gets longer while keeping its density is linked to the large majority of hairs in the growth phase. These, in fact, represent about 90% of the head of hair while the hairs in the falling phase only form 10%. Considering these percentages and the length of the phases, the loss of up to 100 hairs per day is perfectly to be expected.

These observations allow evaluation of the state of a head of hair using special videotrichogram or phototrichogram techniques.
This consists of shaving 1 cm2 of the scalp of an individual, filming or photographing this zone immediately after shaving, then filming or photographing it again two days later. A comparison between the two pictures allows the hairs in the anagen phase to be counted - which will have grown by about 0.6mm - and those in the telogen phase which will not have grown. The anagen/telogen ratio, the hair density and the speed of growth of a head of hair can thus be obtained.
These measurements are interesting for the study of hair in that they vary with many factors such as sex, age, state of health, ethnic origin etc.




WELCOME
PORTRAIT OF AN UNKNOW ELEMENT
LIVING AND RELIVING

GROWING IS COMMUNICATION

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AMAZINGLY NATURAL
SO STURDY AND YET SO FRAGILE
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THE HAIR A SCIENTIFIQUE ENIGMA
HAIR AND CULTURE
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