Hair is made up of Keratin – a fibrous structural protein. Hair also contains natural oils (lipids) and water. These hair “ingredients” are arranged in 3 primary structures: the cuticle (which is the outermost, shingle-like layer); the cortex (the inside of the hair consisting of bundles of protein filaments); and the medulla (a soft spongy-like core in the centre of the cortex)
What are the 3 growth cycles of hair? The growth cycle of hair consists of 3 stages: Anagen – It is the growing period of a hair follicle that typically lasts about 3 to 5 years. Catagen – At the end of the growth period, hair follicles prepare themselves for the resting phase. This stage of the hair growth cycle usually lasts about 1 to 2 weeks. Telogen – This is the resting period of a hair follicle. It is usually 3 to 4 months in length and at the end of this period older hairs that have finished their life will fall out and newer hairs will begin to grow.
The percentage of hair growth in each cycle is: Telogen: 10 – 15% Anagen: 85 – 90% Catagen: < 1%
On average 100 hairs are physiologically shed on a daily basis throughout the human scalp, at random. Certain common events can alter this shedding. For example, during pregnancy more follicles are maintained in the growing phase and there is less shedding than usual. The Hair cycle is also subject to chronological influences. During the autumn months, it is possible that hair shedding may double, whilst during spring shedding is diminished. Both the duration and the daily growth rate of hair is greater during summer when compared to the winter months
By far the most common cause of hair loss in men is “Androgenetic Alopecia” also referred to as “male pattern hair loss” or “common” baldness. Androgenic Alopecia is due to the male hormone DHT acting on genetically-susceptible scalp hair follicles that causes them to become progressively smaller and eventually disappear. This process is called “miniaturization.” The other causes can be Stress, scalp bacteria, poor nutrition, hormonal imbalance, injury and high fever (e.g. Malaria). A very popular procedure for men is a receding hairline treatment or redesign.
The various types of Alopecia are:
The most common form of hair loss in women, Chronic Telogen Effluvium (long-term diffuse hair loss), is an increase in hair loss and a decrease in hair thickness over a long period of time.
Hair grows approximately 10 – 15cm per year In general, the length of any human beings hair is unlikely to grow more than one meter.
Hair color is the pigmentation of hair follicles due to two types of melanin:
With the reduction of Eumelanin and Pheomelanin, the melamine that causes pigmentation in hair, hair turns grey. The loss of melamine causes the hair to turn white.
Shaving your hair doesn’t increase the thickness or quality of the hair. At first it looks thick, as at the roots, the hair looks denser. As the length grows, it looks the same as before.
Each follicle can grow many hairs over a lifetime. On average, each grows a new hair around twenty times.
Hair is strong as a wire of iron. It rips after applying a force equivalent to 60 kg, only after it is stretched for about 70%. A single strand can support 100 grams in weight.
The massive production of the hormone Estrogen during pregnancy puts hair follicles into their ‘growth phase’. After the birth, the hormonal balance is restored and the hair follicles go into the ‘loss phase’, causing a large number of hairs to fall out at once.
The hair quality and growth rate highly depends on the race:
African hair grows more slowly and is more fragile than European hair.
Asian hair grows the fastest and has the greatest elasticity.
African and European people are more prone to balding than Asian people.
What is the average number of follicles per sq. cm in adults? The average number of hair follicles per sq. cm. in adults is 20 to 30 yrs – 615/cm2 30 to 50 yrs – 485/cm2 80 to 90 yrs – 435/cm2
Approximately 85 – 90% of all hairs are in a growing phase at any one time.
Vellus hairs, also known as “peach fuzz” in the urban dictionary, are fine, short, light-colored or translucent, and non-pigmented hairs that develop from childhood and are found on most areas of the body. Their growth is not, in contrast to terminal hairs, affected or dictated by hormones. Vellus hairs are usually no longer than two millimeters, and their follicles are not associated with sebaceous glands.