The hair it's a cylindrical filament, thin and of a horny nature, that is born and grows between the pores of the skin of almost all mammals. The set of filaments is what will make up, for example, the fur of a cat, a dog, among other animals.
Also, the word hair is used to designate the filament that we human beings have, mainly in the head and in other parts of the body.
Hair is a continuation of cornified skin, made up of a keratin fiber and made up of a root or stem. Hair, or human hair, forms in the follicle of the dermis and turns out to be the characteristic feature of thin or thin skin; Each hair consists of a root housed in the hair follicle and a stem that projects upwards above the surface of the epidermis, meanwhile, the papillary area or also called dermal papilla is made up of connective tissue and blood vessels that They provide the hair with the substances necessary to grow.
In humans, hair is distributed over the entire body surface, although there are areas in which it predominates and in others in which it does not exist, such is the case of the navel, mucous membranes and palmar-plantar surfaces. On the head it is in the place where we find the greatest amount of hair, ranging between 100 thousand and 150 thousand.
It should be noted that the hair on the head is somehow different from the rest of the body since the implantation in the skin is much deeper, because the follicle reaches the hypodermis.
Hair does not grow indefinitely but is carried out in a cycle called hair cycle and consists of three phases: anagen phase (the hair is attached to the papilla, it is born and grows, it lasts between 4 and 6 years), catagen phase (This is the transition phase, which lasts about 3 weeks, during which growth stops and separates from the papilla) and telogen phase (rest and hair loss, lasts about 3 months).
The main functions that hair has in the case of humans is:
- the protection of the scalp from the action of the sun and cold;
- the hair of the eyebrows and eyelashes, protects the eyes from sweat; the hair in the nostrils complicates the entry of dust into the nasal cavity;
- also absorbs bumps and scratches.
- And the other function it fulfills is esthetic.
The most common human hair types are: straight, wavy or curly.
Image 1: Fotolia - monica
