Hair has two separate structures - the follicle in the skin and the shaft we see
Except for lips, palms and soles our entire body is covered with hair follicles. All human being have hair follicles below the skin surfaces. Hair follicles are tiny openings in the skin where hair is produced. There are millions of hair follicles covering the human body, and the number of follicles each person has is set at birth.
Each strand of hair grows from a follicle rooted in our skin's subcutaneous tissue. At the bottom of each hair follicle lies a structure called the papilla, which is nourished by tiny blood vessels. The living part of the hair is bottom part of the stocking surrounding the papilla called the bulb. This bottom part is the only part fed by the capillaries. The cells in the bulb divide every 23 to 72 hours, faster than any other cells in the body.
On top of this structure is the root (hair bulb). This is where our hair starts to grow.
Fed by the papilla's blood supply, our hair bulb produces new cells. In fact, the cells in the hair bulb divide faster than any other cells in our body. Newly formed hair cells make their way up the follicle as newer cells form behind them. As they become further removed from their source of nourishment, the cells dry out, harden and die. The dead, hardened cells — made of keratin — protruding from your skin's surface are called the hair shaft.
Hair Cycle
Hair grows from the papilla in different stages in a cyclic activity of the hair follicle. The cycle includes three phases: growth, resting and shedding, also called the anagen, catagen and telogen phases. At any given time, a random number of hairs will be in one of three stages of growth, resting and shedding.
- Anagen Phase: This stage is also called growth stage. Depending on the person’s age and where hair is on the body , a strand of hair might grow for up to 50 weeks.
- Catagen Phase: After growing for up to 50 weeks, a hair guits growing and goes into a resting phase that lasts about 2-6 weeks.
- Telogen Phase: During this phase, hair falls out of the follicle and a new hair starts to grow . The cycle then repeats.
The duration of these different phases, and indeed that of the entire hair cycle varies considerably, depending on the part of the body involved.
For instance, the anagen phase lasts 12 weeks on the upper lip, whereas this phase lasts 15 weeks on the legs. This phase is followed by the telogen phase which may be brief –6 weeks for the lips--- or 6 months for the legs. The full cycle therefore takes 5 months for the upper lip and 16 months for the leg.
It must also be borne in mind that the proportion of hairs in the anagen and telogen phases also differs considerably from one zone to another. Mean values of 60% of anagen hairs versus 40% of teleogen hairs are reported for the upperlip, whereas the corresponding percentages reported for the leg are 25% versus 75% respectively. In this reason results of EPISIVA are seen on the upper lip quicker than on the legs.
The anagen phase is an obvious stage to coping with unwanted hair.
The table below summarizes the wide range of phase lengths and anagen growth.
Hair growth table (after Dr. A de Ramecourt. Pub. Arnette p. 10)
|
Anagen
phase
% |
Telogen
phase
% |
Duration
of the
anagen phase |
Duration
of the
catagen phase |
Duration
of the
telogen phase |
Duration
of the
hair cycle |
Chin |
20 |
80 |
9 weeks |
2-3 weeks |
50 weeks |
15 months |
Upper lip |
60 |
40 |
12 weeks |
2-3 weeks |
6 weeks |
5 months |
Forearm |
40 |
60 |
13 weeks |
2-3 weeks |
16 weeks |
9 months |
Legs |
25 |
75 |
15 weeks |
3-6 weeks |
45 weeks |
16 months |
Pubis |
30 |
70 |
22 weeks |
2-3 weeks |
47 weeks |
18 months |
As the cycles of the different follicles do not coincide, different parts of the body produce hairs of different lengths, depending on the various anagen time periods.
Number of hairs in the anagen phase and the period of hair cycle determine how quickly EPISIVA work. EPISIVA works quicker on the areas where hair cycle is short and percentage of hair in anagen phase is high.
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