Here are the Regrowth Cycles
Hair growth and regrowth
The hair regrowth cycle is the physiological process through which your hair renews itself.
In fact, contrary to what is commonly thought, hair is not always the same from birth to death.
During the lifespan of a human being, each hair on the scalp repeats its regrowth cycle several times:
is born,
it develops,
dies,
is reborn.
and so on...
For this reason, daily hair loss, within certain limits, should be considered physiological.
Losing hair at a rate of 35 per day is average.
Where the number of hairs falling out is significantly higher, the phenomenon should be considered as an alarm bell.
In fact, there are individuals who, boasting thick hair from birth, are subject to physiological hair loss that can reach up to 90/100 per day.
Consequently, hair loss must always be commensurate with the particular characteristics of each individual and is influenced by various factors such as seasonality, genetic heritage and hormonal balance.
If, taking these factors into account, we detect pathological hair loss or obvious scalp anomalies, it is important to intervene in time before the hair follicles atrophy and become unproductive.
A follicle atrophies when it exhausts its number of genetically predetermined hair regrowth cycles.
Considering that the life cycle of a healthy hair varies between 2/4 years for men and 5/6 for women, and that it is repeated up to 20 times over a lifetime, we can well understand how follicles that remain unproductive when you are 20, but also 30 or 40, means that they have significantly reduced the duration of each cycle to the point of becoming prematurely unproductive.
Hair regrowth in the follicles
Rather than follicles, we should always talk about follicular units, since within the follicle the same dermal papilla often gives rise to more than one hair.
Each follicular unit is composed of 1, 2 or 3 (rarely 4 or 5) hair fibres, wrapped in a band of collagen.
Each fiber is equipped with its own erector muscle (which is responsible for the "goosebumps" effect which contracts in the cold and makes the hair straighten) and the related sebaceous glands.
The pilosebaceous apparatus, thus formed, ensures hair growth at a rate of approximately 0.30 millimeters per day.
Unlike animals which have hair loss concentrated in certain periods of the year (moult), in humans the hair regrowth process (anagen, catagen and telogen) is continuous, and the physiological turnover is imperceptible.
In practice, human hair is born, grows and dies according to a rhythm that guarantees a constant percentage of hair throughout the year.
Only in spring and autumn does an "acceleration" of turnover occur (physiological seasonal effluvium).
When the hair reaches the end of its life and falls out, it deposits the dermal papilla at the bottom of the follicle which, after a rest period of approximately 4/5 months, begins a new process of mitosis (splitting of a cell into two cells having the same characteristics) and the hair matrix begins to give life to a new hair and its constituent elements: the epidermis, the cortex and the medulla.
Once the hair bulb is fully formed, the hair is pushed towards the surface of the scalp.
It is usually the new hair, during the growth phase, that pushes out the old hair now at the end of its growth cycle.
This explains the hair we find on the pillow in the morning, the hair that remains on the comb or we lose after shampooing.
As long as the falling hair is replaced by new, healthy hair, the conditions for baldness do not exist, but when the new hair gives rise to an increasingly shorter regrowth cycle, the final outcome is early extinction.
To avoid this event it is necessary to resort to hair regrowth treatments before it is too late.
In the same hair, thicker and more robust hair has a longer life cycle than thinner hair.
Identifying the causes of hair loss therefore means discovering the factors that disturb the regular hair regrowth cycle.
The hair regrowth cycle (or life cycle) is made up of 3 macro phases:
- ANAGENA : Anà = up, above + genà = genesis, birth
- CATAGENA : Katà = down + genà = genesis, birth
- TELOGENA : Telòs = term, end + genà = genesis, birth
1 - ANAGEN PHASE
It is the hair growth phase.
Its duration varies between 2 and 4 years in men, between 5 and 6 in women.
In healthy hair, approximately 85-90% of the hair is in this phase.
The ANAGEN phase is in all respects an active phase because the hair never stops growing.
In this phase the bulb supports a very intense metabolic activity of nourishment and growth.
Furthermore, the dermal papilla is introflexed into the fundamental matrix of the hair and for this reason is directly in contact with the nerve terminals and blood capillaries of the dermis which oxygenate and nourish the hair, supporting its rapid regrowth.
2 - CATAGEN PHASE
It is the phase of progressive suspension of the hair's vital functions.
It lasts about 1/3 weeks, the time needed for the bulb to rise up to the collar and lose the internal epithelial sheath.
The CATAGEN phase is characterized by a rapid decrease in cell division (mitosis), until this function ceases completely and the bulb detaches slightly from the follicle rising towards the surface of the dermis.
In practice, hair growth during the catagen phase is much slower and more decisive.
This phase is easily recognizable because the hair begins to show the first signs of undernutrition: thinning of the bulb in relation to the size of the hair shaft.
Ultimately, the bulb remains connected to the dermal papilla via a fine cell column (the last cells produced by the matrix).
Meanwhile, melanocytes also stop their metabolic activity, while the hair reduces its vital functions to the point of completely ceasing.
3 - TELOGEN PHASE
It is the resting phase of the hair.
It lasts 2/4 months, the hair is still in the hair follicle, but vital activities have completely stopped.
It is a hair that no longer has oxygenation and nourishment from the dermal papilla and remains weakly fixed in the follicle.
Having finished its growth phase, the root of the hair shows a "club"-shaped bulb, very thin and with jagged edges.
To the naked eye this bulb, now atrophic, looks like a pinhead at the base of the hair.
It often alarms patients who believe they have lost the germinative part of the hair, which instead has remained lodged deep in the scalp of the hair ready, if everything proceeds regularly, to start hair regrowth, a new ANAGEN phase.
Hair in the TELOGEN phase is sometimes removed from the scalp by exerting modest traction, without realizing it, such as when scratching the head. In the case of telogen effluvium, hair loss can be truly extensive.
Sometimes hair falls out because it is mechanically stressed by combing, brushing or because new hair in the anagen phase pushes it out of the follicles in which it is located.
If the resting hair is removed mechanically, the follicle interrupts its rest and begins a new anagen early.
Normally, in healthy hair, around 9-14% is in the TELOGEN phase; if this percentage rises to 20% we can speak of a modest and incipient alopecia; while a percentage of 30% means that there is significant alopecia.
It should be noted that in children, as a rule, the percentage of hair in the TELOGEN phase does not exceed 5%.