Comment les cheveux sont-ils structurés et comment poussent-ils

Hair structure and what are the different types of hair?

For many people, hair is a natural adornment and an expression of their personality. But the hair also has protective properties: for example, it protects the scalp from the sun's rays. Eyelashes and eyebrows keep dust, dirt or sweat out of the eyes. The hairs on the nose and ears also protect against intruders.

Hair helps regulate body temperature: if it stands on end in cold weather, it can trap air heated by the body on the skin's surface - like a heating pad.

What types of hair are there?

With the exception of a few areas, for example the palms of the hands and the soles of the feet, the entire surface of the body is covered with hair. We distinguish the fine and short hairs of the body and the so-called long or terminal hairs. It is about the hair of the head, the hair of the beard, the eyelashes, the eyebrows, the pubic hair, but also the hair of the male body, for example on the chest or the abdomen.

 

Hair distribution varies from person to person and depends on age and gender. For example, in children the body is mostly covered with fine hair. In adult women, 30% and in men about 90% of the body surface is covered with long hairs.

What is the structure of the hair?

Each hair consists of a rod and a root. The shaft is the visible part of the hair that protrudes from the skin. The hair root is located in the skin and extends into the subcutaneous tissue. It is enclosed in the skin and connective tissue - the hair follicle, which also contains a sebaceous gland.

 

A small muscle is also attached to each hair follicle, which helps lift the hair. Many nerve fibers also end at the hair follicle. This allows us to perceive the movement of the hair and even feel a light breeze.

 

At the lower end, the hair root presents a spherical thickening which is called the hair bulb at this point. The "capillary papilla", a well-perforated module, extends into the hair bulb from the bottom. At the border between the papilla and the hair bulb, new hair cells are constantly being produced.

How does a hair grow?

It grows from its root, which grows under the scalp into a small pocket, called a hair follicle. It emerges from the root through the papilla, which is located at the base of the root and through which the blood arrives and nourishes it. It is therefore the "raw material" contained in the blood that allows hair to grow. In a second phase, the blood passes from the papilla to the matrix, where the reproductive cells of the hair are located.

 

A hair grows about an additional centimeter per month. Beard hairs, but especially eyelashes, eyebrows and body hair grow more slowly.

 

Whether the hair is straight or curly is related to the section of the hair. If it is flat, the hair grows smooth on the skin. The more oval the section, the more curly the hair.

 

The color of the hair is due to the different content of the pigment melanin in the keratinized cells. It can vary greatly from person to person and change throughout life. With age, the melanin content decreases in most people, and at the same time more air is trapped in the hair - it loses color and turns white.

What is the hair cycle?

Depending on where the hair grows on the body, the growth phase varies in duration: for scalp hair, for example, it can last for several years. Therefore, if not cut, the hair can grow to a length of over a meter. The growth phase is particularly short for eyelashes, eyebrows or the hairs at the entrance to the ear and nose. They only grow for about 100 to 150 days. This is why these hairs cannot grow so long.

 

At the end of the growth phase, the hair root detaches from the papilla. This stage is called the transition phase and lasts about two to four weeks. When the hair is completely detached from the papilla and therefore from the blood supply, the hair's resting phase begins - also called the telogen phase. The hair is slowly pushed out of the skin and eventually falls out. The rest phase can last several months.

 

At the base of the "empty" hair follicle, the hair cells begin to multiply again and assemble to form a new hair: A growth phase resumes and the hair cycle begins again.

When does hair loss increase?

Since hair always goes into a resting phase and then falls out, a person is constantly losing hair. A healthy adult can lose about 70 to 100 hairs per day. However, since new hair is always growing back at the same time, this natural hair loss goes unnoticed.

 

However, if the hair roots are damaged during the growth phase or if a lot of the hair goes into the resting phase at the same time, the hair loss is more severe (effluvium). If no new hair grows, baldness appears. Whether the affected area is small, whether it is the entire scalp or body hair, this baldness is called alopecia. Some forms of alopecia may go away and the hair grows back. However, baldness can also persist - a prime example is permanent baldness in men.

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