And whether you know...
About a structure and functioning of hair
In spite of the fact that we got used to perceive hair of the person as an esthetic factor, actually from the point of view of anatomy hair are a component of a protective cover.
Structure of hair
At each hair — a special structure. The external cover of a hair is made by keratinaceous scales which are imposed at each other. That part of each hair which is over an integument is called a core. Structure of hair of the person three-layered. The periblast which is also called a cuticle, is urged to carry out protective function. It is formed by the thin scales blocking each other. Respectively, a structure of hair of the head of the person such is that if these scales are laid densely and correctly, then hair at the person soft, streaming and shining. Both on a photo, and in life they look live and beautiful. At the same time at damage of cells of a cuticle (them both physical, and chemical influence can damage) hair cease to shine, very easily are confused and break.
The following layer of a hair — korteks, located under a cuticle. This cortical substance which gives to elasticity to a hair. In a korteksa there is a special pigment melanin which defines what will be an individual hair color at the specific person. In each hair there is a marrow which is made by keratinaceous cells and air-vessels. According to scientists, the structure of a core of hair assumes that on this layer useful nutritious elements to other layers of a hair arrive. In more detail to consider features of a structure of a hair, the special graphic scheme can be used.
It is accepted to call the part of a hair which is under skin a hair root (also it is called a hair bulb). Structure of a root of hair following: the hair root is surrounded with a hair sack which name — a follicle. From what form of a follicle is observed at the person, features of his type of hair depend. So, from a round follicle at the person a straight hair, and hair of a little curling type grow grow from an oval follicle. At those people who can brag of curly hair, follicles reniform.
From what structure of skin and a hair at the person, depends the general condition of hair. So, the natural hair shine defines amount of own fatty greasing which the special antiseptic agent enters. In an integument there are sebaceous glands which secret is allocated in hair follicles. Thus protection of a trunk of a hair is provided. Therefore functions of hair of the person depend also on that how qualitatively such greasing protects each hair.
But sometimes sebaceous glands produce too much secret. It can occur as a result of surge in hormonal activity, and also owing to other factors. As a result hair of the person become very fat. On condition of low products of such secret hair, on the contrary, become too dry.
As hair grow
That part of a hair which grows from under an integument of the person consists of dead fabric. The growth cycle of hair proceeds several years. After old hair drop out, the new cycle begins again.
Process of growth of hair is divided into three stages. At the first stage of hair grows actively. The second stage of growth call intermediate: at this time the hair does not grow any more, however nipple cells still function. At the third stage growth of a hair completely stops. Functioning of hair is arranged so that as a result of growth of a new hair old drops out then the new hair passes all cycles again.
The first stage of growth of a hair can last 2-4 years, the second — about 20 days, the third — till 120 days. If to estimate all hair of the person in general at some point, then about 93% of hair stay in the first growth phase, 1% of hair endure the second growth phase and 6% of hair — a third. Head and body hair can repeat growth cycles throughout human life of 24 — 25 times.
Hair grow on all body, an exception are only soles and palms. The adult on a body has about 100 000 hair. The number of hair depends on what they are colors. So, most of all body hair at blondes.
Hair begin to appear at the person on the third month of pre-natal fetation. On a body the uneven growth of hair is noted. Most slowly eyebrow hair grow, their most rapid growth is noted on the head. In three days head hair can grow by 1 mm. Normal in days at the person 50-100 hair can drop out. The hair loss in normal quantity is physiological process. Most quicker hair at the person grow in the flying and in the spring.
Properties of hair
97% of protein (keratin) and 3% of moisture are a part of each hair. The keratin is a proteic matter which includes sulfur, vitamins, microelements. Several types of hair which grow on a body of the person are defined. Long hair are the strongest and grow on the head, and also those are hair of a beard, moustaches, generative organs, armpits.
Hair setaceous are the hair growing in a nose and ears, and also an eyebrow, eyelashes. Hair vellus grow on integuments of hands, legs, trunks, persons.
Healthy hair are elastic and have high margin of safety. The healthy hair easily stretches and can sustain up to 200 g of loading. Hair of the person are hygroscopic: they easily absorb moisture. They show resistance to effect of acids, however very badly react to alkalis.
Most of all hair is located on a calvaria of the person. Eyebrows on average contain about 600 hairs, and eyelashes — about 400.
If functioning of hair is defined by their properties, then color depends on how two types of melanin correspond: eumelanin and feomelanin. These types of melanin are distinguished by a form of granules: at an eumelanin of a granule extended, and a form of granules of a feomelanin oval or round. Therefore, eumelanin call the granulated pigment, and feomelanin — diffusion. All hair contain two types of pigments in different ratios. Therefore, people have three different hair colors: red, blondes and brunettes. And here it is much more shades of a hair color: them is to 300.
Functions of hair
Function of a hair is very important for the person. First of all, hair are ornament, that is carry out esthetic function. They can both emphasize the dignity of the person, and to hide his shortcomings. However not only esthetic functions carry out hair of the person. They help to avoid both overcooling, and a head overheat. In hair the air layer which helps to keep as warmly, and cold is created. Vellus hair which are located on a body take part in touch processes. Hair which grow in ears and a nose help to detain dust. Eyelashes of the person help to protect eyes. Those hair which are located armpits allow to reduce friction force. Therefore, the person makes any movements, and skin at the same time is not injured. Besides, in hair some substances can collect. This their function is successfully used by criminalists in the course of work.
In general functions of hair at mammals are reduced to providing heat insulation, protection of integuments against external influences, ensuring coloring (at animals it is about masking and attractiveness). Besides, animals have special hair which allow them to be guided in a scope, that is they are responsible for sensitivity. But in the course of evolution hair of the person partially lost such functions.