To complete the physiology of this appendage of the skin it is important to mention for its physiological functions the sebaceous gland, responsible for the production of sebum, the erector muscle which contracting causes the hair to straighten (orropylation) and the melanocytes that have the role of “coloring” the hair bark with melanin production.
Focusing on the parts of the hair we can distinguish:
the STELO or FUSTO. It is the visible part outside the follicle
the ROOT. It is the non-visible part immersed in the follicle
the BULB. It is the vital and deepest part that contains the germinative cells.
Therefore cutting the short hair, unfortunately, does not lead to the strengthening of the structure because what is cut is only the part of the stem devoid of any vital activity. The advantage that can be had is of a different nature, in fact in this way it is possible to reduce the trauma due to brushing, heat treatments, and washes.
The hair cannot, therefore, be compared to a plant that needs constant “pruning”!
The germinative cells of the bulb as they reproduce push the previously formed cells to the surface, which gradually lose their vitality, enriching themselves with an important insoluble protein in water: KERATIN.
In this process, the cells become rigid, atrophic and lacking in metabolic activity.
Keratin gives resistance to both atmospheric agents such as heat, cold, humidity and solar radiation, and to external aggressions due to chemical treatments and air pollution.
The keratinization of the stem can be altered by nutritional deficiencies and/or metabolic defects related to hormone production.
These situations can cause an abnormal keratinization process with consequent structural dysfunctions on our hair.
LIFE CYCLE OF HAIR
But how long does a hair live?
Those of us who have never bothered to see their hair destined for the drain pipe fall onto the shower tray … but often this is a normal turnover of the hair’s life cycle.
To give some numbers we can say that in a young person the amount of hair varies from 90,000 to 150,000 while it drops to around 80,000 with age.
In the follicle periods of growth and rest alternate, but we see in detail how the cycle of one of our hair can be divided:
anagen phase or growth: it is characterized by the intense activity of the cells of the bulb and has a different duration depending on the sexes. In humans it is about 1000 days, in women, it can even reach 5,000 days. This explains the difference in hair length between the sexes.
catagen phase or decreased activity: it is the intermediate phase of the vital process in which keratinization begins and the progressive loss of vitality of the metabolic activity of the cells of the matrix.
telogen or resting phase: this is the last phase during which the hair, although dead, remains anchored to the hair follicle for some time. If at this stage modest traction is exercised the hair is removed without pain.
You don’t have to worry if you find yourself part of your hair between the teeth of the comb: in reality, the germinative part is left alive and grows deep in your scalp and ready to start a new cycle.
The aspect that makes us different from other mammals is precisely this “replacement” that occurs in humans “as a mosaic”, which means that each follicle manages its life cycle independently of its neighbors. Fortunately, there are no periods of molting (in which there is a massive loss of fur with a change of fur!).
It must be said, however, that in certain periods of the year, including autumn and spring, there are “accelerations” of the life cycle of the hair, which are defined by the experts as “seasonal physiological effluvium”.