For many, hair can be a cause for concern and sometimes jealousy. For some, it is also a source of vanity. If people have correct information and facts about hair, it will save a lot of worry or jealousy.
An average person has up to 150,000 hair follicles on the head, while the entire adult body has 5 million. That number is constant throughout life. Hair has two different structures: the follicle itself, which resides in the skin, and the shaft, which is what you see above the scalp.
Hair follicle – The hair follicle is a tunnel-shaped part of the epidermis that extends into the dermis of the skin. At the base of the follicle is the papilla, which contains capillaries or tiny blood vessels that nourish the cells. The living part of the hair is the lower part that surrounds the papilla, called the bulb. Bulb cells divide every 23 to 72 hours, notably faster than any other cell in the body. Only one hair grows from a follicle. At the base of the hair follicle there are sensory nerve fibers that envelop each hair bulb. Bending the hair stimulates the nerve endings allowing a person to feel that the hair has moved.
The hair follicle has two sheaths that protect it and help form the growing hair shaft. There are several other structures associated with the hair follicle, including the arrector pili, which is a small bundle of muscle fibers connected to a follicle. The contraction of these muscles is what causes goose bumps. The sebaceous glands are also attached to the hair follicles, which produce an oil, called sebum, that lifts the hair follicles to the surface of the skin, where it lubricates the skin and hair.
Hair shaft – The hair shaft is made of a tough protein called keratin and is made up of three layers. In fact, hair is not a living structure as this protein is dead. The inner layer of a hair is the medulla, the second layer the cortex and the outer layer the cuticle. The cortex makes up most of the hair shaft. The cuticle is a compactly shaped structure made of overlapping shingle-shaped scales. Both the cortex and the medulla are those that contain the pigment of the hair and give it its color.
Hair growth cycle –
There are four stages of the hair growth cycle:
• Anagen (Growth phase): Hair in the anagen phase can grow faster during the first few years. The average growth rate is 1 to 1.5 cm every 28 days. This phase lasts from two to seven years and determines the length of our hair.
• Catagen (Regression phase): This stage lasts about ten days. The hair follicle shrinks and becomes detached from the dermal papilla.
• Telogen (Rest phase): This is the resting phase of the follicle that lasts for about four months. Approximately 10 to 15% of the hair is in this stage. The follicle remains inactive in its shortened state and awakens to regenerate with the onset of the new growth phase.
• Exogenous (Shedding phase): this is the period when the hair reaches its terminal position in the follicle. Hair at rest gradually becomes loose resulting in falling out. Most of the shedding occurs during the new growth phase.
Over time, the duration of the anagen stage decreases. Therefore, the hair can become weaker and thinner after each cycle. That is why it is important to ensure that your diet is rich in specific nutrients to maintain normal and healthy hair growth.
If the hairs enter the resting phase too early, it can lead to excessive shedding and noticeable thinning of the hair.
Telogen effluvium –
Telogen effluvium is a phenomenon that occurs after pregnancy, major surgery, drastic weight loss, or extreme stress, in which people lose large amounts of hair every day, usually by shampooing, combing, or brushing. It can also be a side effect of certain medications, such as antidepressants, beta-blockers, and non-steroidal anti-inflammatory drugs. During telogen effluvium, hair changes faster than normal from its growing phase to the resting phase before rapidly moving into the shedding or telogen phase.
The bottom line –
Hair is much more complex than most of us understand. In addition to creating gender identity, it plays a vital role in the appearance of both men and women. Therefore, any objective information about hair will help people to take good care of it.