Hair Growth Cycle
The healthy hair growth cycle
Hair consists of Keratin, which is a special protein that also produces toenails and fingernails. The protein also forms the outer protective layers of the skin, while effectively protecting it from foreign elements and intrusion. Similarly, hair also possesses an outer layer called the cuticle. The two remaining layers include the medulla and the cortex. The cuticle is both colorless and thin, and serves to protect the cortex, which consists of melanin. The latter is solely responsible for the color of hair, and differs from individual to individual. The melanin is based within the thicker cortex, and consists of two types. This includes eumelanin, which creates black or brown hair. The other is type is called pheomelanin, which produces reddish hair.
Blonde hair grows because of little to no melanin, while grey hair grows from a lack of melanin as well. Grey hair can also form from severe stress, age, or medical illnesses. To understand how hair grows, you also have to look at is innermost layer. This is called the medulla, which effectively reflects light and is responsible for various hair tones. This is the primary reason why hair looks different in sunlight, as opposed to darker or shaded areas. The cortex is responsible for the shape of the hair growth. For example: if the cortex’ cross section is round, you will grow straight hair. If, however, the cortex is oval in shape, you will grow wavy or curly hair.
1. Anagen Within the Anagen phase, the growth cells in the papilla divide and form the hair shaft. The shaft is then keratinized, as it makes its way up out of the follicle and into the pore. Simultaneously, the follicle grows into the deeper levels of the skin to secure nourishment. As a result, individuals that have extended anagen growth rates can grow very long hair. Those, however, with short growth phases can only grow short hair. Hair grows at approximately ½ inch per month. Therefore, if left uncut, it can grow to between 12 and 48 inches in length.
2. Catagen This is a brief two to four week cycle; which is also referred to as the transitional phase. As part of the hair’s renewal process, the hair stops growing due to a degraded follicle. The hair, however, does not completely fall out. The follicle simply shrinks to about 1/6th of its normal length. As a result, the lower part is destroyed, while the papilla breaks away and the bulb is detached from the blood supply. The hair shaft is also pushed up as the follicle simply dissipates.
3. Telogen The follicle’s Telogen phase lasts for about two to four months. During this period, the hair growth remains dormant; however, it remains attached to the follicle. The papilla is simply in a resting stage, which results in 10-15% of hairs resting as well.
Once the Telogen phase expires, the cycle is considered complete. The hair then goes back into the Anagen phase, and the process is repeated again. As the hair reverts back to its original phase, the shaft begins to form and the old hair is simply pushed out or lost. According to hair growth experts, humans lose anywhere between 50-100 hairs on a daily basis. This is part of the hair’s natural growth process, and can result from hair combing or showering. In healthy follicles, however, new hairs will soon replace these lost hairs. Permanent or temporary hair loss can stem from a myriad of factors. This includes stress, tension, skin disease, thyroid disease, or excessive exposure to chemicals. Other factors include hormonal and nutritional issues, along with medication, chemotherapy, radiation, or existing health and medical issues. Contrary to popular myths and beliefs, hair growth cannot be stopped as a result of close haircuts or excessive trimming. While it might take the hair a little longer to grow back, it will simply follow its natural cycles and stages.
If hair enter the Telogen phase too early, excess shedding and noticeable thinning of the hair can occur.
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Miniaturisation is the technical term given to the shortening of the Anagen phase of the hair growth cycle. For many people the length of the Anagen phase shortens every cycle resulting in hair growing slower, becoming weaker and appearing less vibrant.
Many treatments work by increasing the duration of the Anagen phase or reducing the resting phase.
(1) Healthy Hair
Healthy Hair is maintained when the scalp receives a sufficient blood supply thus achieving the ideal environment for healthy hair growth.
(2) Hair Hardens
Keratinisation Zone – results in the hair hardening.
(3) Vellus Baby Hair
Vellus Fine Baby Hairs are a result of the miniaturisation process. The hair follicle has shrunk to the stage where it is no longer receiving the required nutrients and oxygen rich blood supply.
This can be due to toxins building up in the body causing the hair to become weak and prone to sebum blockage.
Miniaturisation of Hair Follicles can be recognised by receding hairlines and male and female pattern baldness.
Excessive hair shedding
When the hair enters the resting phase early it results in excess shedding and ultimately noticeably thinning hair. This does not become noticeable until approximately 50% of hairs have been shed. This is because each hair is in a different stage of the hair growth cycle which can take years.
It is normal to shed around 100 hairs per day so identifying excessive shedding is difficult. Most people notice more shed hairs than normal when washing their hair, on their pillow in the morning or when brushing their hair.
A wide range of factors can impact on the health of the hair, hair shedding and hair growth. These factors can prevent the body from efficiently absorbing the essential nutrients from food and are often lifestyle related.