The Hair Growth Cycle
Hair grows from the follicle, or root, underneath the skin. The hair is ‘fed’ by blood vessels at the base of the follicle, which give it the nourishment it needs to grow. Between starting to grow and falling out years later, each hair passes through four stages: anagen, catagen, telogen and exogen. Every hair is at a different stage of the growth cycle.
Over time, the length of the anagen stage decreases. Therefore, the hair may become weaker and thinner after each cycle. That’s why it’s important to ensure your diet is rich in specific nutrients to maintain normal, healthy hair growth.
- Anagen (Growing Phase)
The growing phase lasts two to seven years and determines the length of our hair.
- Catagen (Transition Phase)
This is the transitional stage that lasts about ten days. The hair follicle shrinks and detaches from the dermal papilla.
- Telogen (Resting Phase)
This is the resting phase which lasts around three months. Around 10-15 percent of hairs are in this phase. Whilst the old hair is resting, a new hair begins the growth phase.
- Exogen (New Hair Phase)
This is part of the resting phase where the old hair sheds and a new hair continues to grow. Approximately 50 to 150 hairs can fall out daily, this is considered to be normal hair shedding.
THERE ARE 3 MAIN TYPES OF HUMAN
HAIR LANUGO, VELLUS AND TERMINAL
Lanugo hair – is very thin, soft, usually unpigmented, downyhair that is sometimes found on the body of a foetal in the womb or newborn baby. It is the first hair to be produced by the feta’s hair follicles, and it usually appears around sixteen weeks of gestation and is abundant by week twenty. It is normally shed before birth, around seven or eight months of gestation, but is sometimes present at birth. It disappears on its own within a few weeks.
It is replaced by hair covering the same surfaces, which is called vellus hair.This hair is thinner and more difficult to see. The more visible hair that persists into adulthood is called terminal hair.
Vellus hairs –are a type of human hair that are fine, short, light-coloured or translucent, and non-pigmented 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 hair is the technical term for “peach fuzz” which is what it is called in the urban dictionary. Peach fuzz usually refers to the light and sparse hair found on the upper lip of most young boys. Vellus hairs are usually no longer than two millimetres, and their follicles are not associated with sebaceous glands. The shafts of vellus hairs are roughly the same or smaller than their internal root sheaths while the bulb of the follicle are located at the upper dermal part of the skin.
There is some evidence indicating a connection between the activity of sebaceous glands and the growth of vellus hairs. Since vellus hairs have no underlying sebaceous glands, pre-pubertal children do not develop acne and other skin conditions which are associated with these glands. Vellus hairs can be more prominent on females and children because they do not have as many terminal hairs as adult males, which tend to obscure vellus hairs.
Terminal hairs – are thick, long and dark, as compared with vellus hair. During puberty, the increase in androgenic hormone levels causes vellus hair to be replaced with terminal hair in certain parts of the human body. These parts will have different levels of sensitivity to androgens, primarily of the testosterone family (male hormones).
The pubic area is particularly sensitive to such hormones, as are the armpits which will develop axillary hair. Pubic and axillary hair will develop on both men and women, although males will develop terminal hair in more areas. This includes facial hair, chest hair, abdominal hair, leg and arm hair and foot hair. Human females on the other hand can be expected to retain more of the vellus hair.
DIFFERENCES BETWEEN VELLUS AND TERMINAL HAIR
Vellus Hair is short, thin hair that has little colour, and is barely noticeable. You’ll see it most in childhood (not the same as lanugo hair on foetuses). Terminal hair is mature hair. Thick, strong and pigmented (or grey). This is hair on the head, pubic, under arms, face of men. The growth of terminal hair is influenced by hormones.