The hair grows from the hair follicle housed in the hypodermis, and for this reason the distance between the point of emergence of the hair on the scalp and the hair can be up to a centimeter. The sebaceous gland, instead, engages in the hair follicle in the dermis, near the epidermis and close to the surface of the scalp. The union of the hair follicle with sebaceous gland creates pilosebaceous apparatus.
Healthy hair and naturally developed are composed of three parts:
The analysis by mineralogramma shows that hair consist mainly of keratin and, to a lesser extent, of other three substances: melanin, lipids and minerals.
The Keratin, responsible for the strength, elasticity and plasticity of the hair, exists in two main forms:
The last one, has an helical shape, is fibrous and insoluble in water, and it is the predominant form in the composition of the skin and hair, as well as in the nails and in the enamel of the teeth. The hair is formed by keratin in a percentage between 65% and 96%. Inside the hair follicle, the hair germ cells, during the ascent to the skin and the scalp, driven upward by the rising new cells, undergo the process of keratinization, which is essential for the formation of the hair. The process of keratinization of hair is governed by hormones, vitamins, genetic and metabolic factors. Consequently, dietary deficiencies, or enzymatic defects of metabolic pathways of cholesterol and fatty acids synthesis, can lead to abnormalities in the keratinization process thereby leading to a weakening of the hair, and other structural defects of the hair shaft .which are due to weakening of the hair and other structural defects of the hair shaft.
Melanin
The melanin in the hair is distributed in granular form, and it is the pigment responsible for hair and skin color. Melanocytes synthesize two different types of melanin: eumelanin (brown-black) which is located in dark hair and pheomelanin (reddish) located in blond and red hair. Consequentely the full range of colors human hair derives from a different combination of these two types of melanin. The white or gray hair, leading to hair graying with age, are the result of the gradual reduction in the activity of melanocytes.
The skin lipids, in particular those located on the scalp, are composed for 75% of lipids produced
by the sebaceous glands and for the remaining 25% of lipids derived from epidermis. The lipids in the hair are mostly derived from those of sebum. Originally lipids in the sebum contain: triglycerides, waxes, squalene and sterols, but within the hair follicles are contaminated by corneal cells, water, diglycerides, monoglycerides and free fatty acids.
The sebum with its lipids protects and lubricates both the scalp that the hair. When the sebaceous glands do not produce enough lipids there is a problem of dry skin of the hair.
Scientific studies show a direct relationship between the amount of trace elements present in the blood and the amount of those present in the hair and keratin, but also between their quality and the color of the hair, in particular:
Generally, the lack of mineral salts makes the hair bulb small and unsuitable to produce sufficient amounts of keratin, thus leading to having thin hair. The main chemical elements present in the hair are:
The cycle of hair growth and regrowth is a physiological process through which the hair is renewed. In fact, during the life of a human being every hair on the scalp repeats its growth cycle many times: born, grows, dies, and reborn. For this reason, the loss of hair daily should be considered physiologic, and should always be proportionate to the particular characteristics of each one and it is influenced by many factors such as seasonality, genetic and hormonal balance.
The cycle of hair growth (or life cycle) consists of 3 phases:
Anagen Phase – Active growth phase (2-6 years)
It is the growth phase of the hair. It lasts from 2 to 4 years in man, and from 5 to 6 years in woman. In healthy hair approximately 85 to 90% of hair is in this phase. The anagen phase is an active phase because the hair never stops growing. In this phase the bulb has a very intense metabolic activity of nourishment and growth. Moreover the dermal papilla is inserted in the fundamental matrix of the hair, directly in contact with the nerve endings and blood capillaries of the dermis that provide oxygen and nutrients to the hair, supporting their rapid regrowth.
Catagen phase – Transition phase (1-2-weeks)It is the phase of progressive suspension of vital functions of the hair. It lasts about 1-3 weeks, during which time the bulb goes up to the collar and loses its inner epithelial sheath.
The catagen phase is characterized by a rapid decrease of the cell division (mitosis), until its complete stop when the bulb detaches itself slightly from the follicle up towards the surface of the dermis. During the catagen phase hair growth is much slower and decisive. This phase is easily recognizable as hair begin to show the first signs of undernutrition: thinning of the bulb, in relation to the size of the hair shaft. At the end, the bulb is connected to the dermal papilla through a thin column of cells. Meanwhile, even the melanocytes stop their metabolic activity, while the hair reduces its vital functions until either stop completely.
It is the resting phase of the hair. It lasts 2-4 months, during which the hair is still in the hair follicle, but its vital activities are completely stopped. The hair has more oxygen and nutrients from the dermal papilla and remains weakly driven into the follicle. The hair has completed its growth phase, and the root of the hair shows a bulb shaped like a “club”, very thinned and with jagged edges. This bulb has become atrophic, and it looks like the head of a pin at the base of the hair. This situation often alarming patients who believe they have lost the part of the hair follicle, which instead has remained deeply in the skin of the hair ready, if all goes well, to start the regrowth of the hair, a new anagen phase.
Usually in healthy hair, about 9-14% is in the telogen phase, if this percentage increases to 20% is a small and incipient alopecia, while a percentage of 30% means that you are in the presence of a strong alopecia . It should be noted that usually in children, the percentage of hairs in the telogen phase does not exceed 5%, and that’s why their hair grows abundant.
Sanità