hair physiology

      

 Hair is composed of root, under the skin (dermis), and strain, the outer part (your hair itself). The root consists of cells that are renewed gradually. At the basis of the root of hair is a germ called follicular bulb. It has a cavity (the hair papilla) that contains nerves and blood vessels and serves to nourish the hair. In continuation of hair papilla, strain is formed by multiplying the bulbar germ cells. Papilla dysfunctions lead to hair loss.

Space where is implanted the hair shaft is called follicle or root. Together with the hair shaft, it forms the hair follicle whose shape and curve determines the appearance of hair (straight, curly or wavy).

Together with sebaceous gland, hair follicle formed the pilosebaceous follicle. The orifices of pilosebaceous follicle are pores.

In the follicle, keratin is produced. It is a tough substance that gives hair shaft strength and form. Keratin is composed of oxygen, hydrogen, carbon, sulfur, sodium and nitrogen and it is resistant to high temperatures, acids and enzymes. Also, keratin is of two types: stable (the right keratin) and unstable (the loop keratin). Under the influence of certain physical factors (heat, moisture) or chemical (oxidizing substances) the two keratins merge, leading to curl of hair.

In section, the hair shaft is composed of three layers:

- External stratum corneum (the cuticle) is made ​​up of dead cells, arranged in the form of scales, which protect the hair and gives it strength.

- Pigmentary layer (cortex) is composed of cells that give hair color.

- Marrow, located in the center, which consists of large cells with defined shape.

Hair color is hereditary as skin color. In the follicle epithelium the pigment is located. It is composed of melanin that determines the hair color. It can be black or brown, that gives hair a black, gray or brown color or it can be yellow or with a reddish pigment. The mixture of these pigments determines the natural hair color.

Hair whitening is caused by the air penetration in the strain.

Hair grows by about 0.3 mm per day. The lifetime of the hair is 2-4 years, depending on geographical region.

Hair falls daily (40-50 shafts per day in healthy individuals and up to 100 shafts to the elderly) but it regenerates. When the season changes (especially in spring and autumn) the amount of hair shafts falling is greater.