TYPES OF HAIR
Depending on a person’s age, gender, body part and certain morphological characteristics hair can be distinguished according to the following categories:
This is the first downy hair, which are produced during intrauterine life from the embryonic follicles. This type of hair is soft without medulla and usually with no colour. During the 7th and 8th month of life in utero this type of hair falls. This first generation of hair can be observed in premature infants as well as in some pathological conditions, such as alopecia areata.
The second generation of hair that are rarely longer than 2 cm and remain soft without medulla and may have colour or not.
Vellus hair that is present during childhood starts changing, having more colour and medulla. This change lasts until puberty in all areas of the human body.
During puberty, hairs become gradually longer and thicker, while their colour changes too.
On the head changes may be observed in terms of hair colour and shape.
This change to terminal hair is completed faster on the eyelids as compared to the other areas of the body.
During puberty, androgens contribute in the increase of hair change rate. The hair of the armpits and pudenda becomes more thick and the hair shaft becomes spiral or it rotates around its axis with a final length which can reachs up to 6 cm.
As far as boys are concered, terminal hair appear firstly on the upper lip area, then on the cheeks and finally on the rest of the body. In men hair develop on the upper abdomen, buttocks, chest, arms and shoulders.
The percentage of hair follicles which will develop and produce hair in men is approximately 90%, while the relevant percentage for women is 35%.