The hair on the 3% consists of water, and 97% of the protein. Protein substance – keratin enriched with sulfur, trace elements (iron, copper, zinc, chromium, manganese) and vitamins (A, B, F, G, T).
Hair can be of different types:
- long (head, beard, mustache, armpits, genital) – is the strongest hair.
- bristly (eyebrows, eyelashes, hair in the nose and in the external ear canal);
- vellus (on the face, trunk, extremities).
The hair shaft consists of three layers. The core of the hair is called the medulla, it contains dead cells. Medulla is not in the baby hair and the other ends of the hair. The bulk of the hair is its cortical substance, composed of elongated, closely contiguous cells containing pigment – a coloring agent. The pigment may be red, yellow and black, and the combination of these colors creates a unique hair color. In the absence of pigment the hair looks white. The outer layer of the hair – the cuticle, the skin – is represented by a flat keratinized cells, which, being located in a single layer, overlapping each other like shingles.
The root of the hair follicle is located in that expands on the skin of a small extension. In the skin follicles around the border of the outer and middle third of the hair falls into the excretory duct of the sebaceous glands. Hair fitted with smooth muscles, having a form of tape at one end by a short tendon attached to the compact layer of the dermis, the other – to the point below the confluence of the mouth of the sebaceous glands. Shortening, the muscle lifts the hair and squeezing at the same time the sebaceous glands, promotes the release of her secret.
Hair growth in humans occurs in cycles. The cycle lasts for years, and then a few months, a period of rest, after which the old hair falls out and begins a new cycle. The fastest growing hairs on the head (3 days – about 1 mm), the slowest of the eyebrows. A single hair grows an average of several months to 6 years. Lashes live from 3 to 5 months., Vellus -7-10 months. It is normal if the day falls on his head from 30 to 50 hairs.
As the hair papilla zapustevaet, onion cells coarsen, and the bulb turns the hair bulb, similar to an inverted fir cone. If at the end of the hair has fallen spike, then it indicates a normal rate and that the hair is healthy. If you are at the root of the hair yanked a subdivision or a seizure, then the hair of pathologically altered. Such hair is breaking up, their growth is weak, with the appearance of the skin surface, they break off. Flask-shaped hair falls out at the physiological changes of hair on its place grow new hair, or the remainder of the newly formed papillae. In diseases of the hair, this process is absent, and the hair falls out completely.
Hair grows all over the body except the palms and soles. In the adult of about 100,000 hairs, and their number depends on the color. Have red hair, very thick, but less than brunettes. Most hair blond – approximately 150 000. Hair in African-American are the largest of all, can be 3 times thicker than the light. Arranged his hair is uneven: more of them on the crown, less on the part of the temporal and forehead.
Healthy hair is usually strong and elastic. Hair can be stretched to the fifth of its length, and then he returns to his condition. On the strength they are comparable to aluminum and can withstand loads of 100 to 200 have hair hygroscopic, that is able to absorb moisture. They are quite resistant to acids rather weak, but can not tolerate alkaline compounds.
For a person hair played a big role. First, they are wonderful decoration, allowing to emphasize glamor, to hide the flaws, and, secondly, they perform several important functions – the hair protects the head from overheating and from hypothermia. Vellus hairs are involved in touch, eyelids protect the eyes, hair, nose and ears retain dust.
