Healthy Curls

Hair Science

Where Hair Begins

Hair science is fascinating! Did you know that a 22 week old fetus has all of its hair follicles formed?  In fact on average that fetus will have about 5 million hair follicles on its body. Whoa! This is the most hair follicles a person will ever have, as new hair follicles are not generated during life. In fact hair density is reduced as we grow up because our scalps expand too.

hair foliclesHair Follicles

Our hair has two separate structures. One is the follicle in the skin, and the other is the visible shaft. A hair follicle tunnels through the epidermis and into the dermis. The follicle has several distinct layers and each one has its own purpose. At the base of the follicle is the papilla. The papilla is full of capillaries, or minuscule blood vessels that feed the cells.

The part of the hair that is living is at the bottom surrounding the papilla. This is referred to as the bulb. The cell growth of the bulb is faster than any other cell growth in our bodies. The bulb cells divide every 23 to 72 hours.

The follicle is covered by two sheaths, an inner and outer. These sheaths protect the growing hair shaft. The inner sheath grows within the hair shaft to the opening of a sebaceous (oil) gland, and now and then an apocrine (scent) gland. The outer sheath goes all the way up to the gland. The pili muscle is attached below the gland around the outer sheath. This erector muscle contracts which makes hair stand and makes the sebaceous gland to secrete oil. The sebaceous gland is essential as it manufactures sebum. Sebum helps form the hair and skin. As we grow older age we make less sebum. Sebum production in women decreases much faster than in men.

The Hair Science Growth Cycle

When you understand the hair growth cycle you can be aware of issues that might arise with your hair. There are three stages of the hair growth cycle:

  • Anagen
  • Catagen
  • Telogen

Anagen Phase

Hair will generally grow about half an inch each month. In seasonal climates hair grows faster in the summer than in winter months. This anagen growth phase is about 3 to 5 years. This means full length hair is about 18 to 30 inches. In Asian people this phase can last as long as 7 years.

Catagen Phase

After the anagen phase, hair enters the catagen phase that lasts only about 10 days.

Telogen Phase

Then hair enters the telogen phase, where growth subsides and hair is released or falls out. The follicle is then inactive for 3 months. After that the follicle returns to the anagen phase and this cycle starts again. Every hair follicle is independent and in its own place in the growth cycle.  That is why your hair does not naturally all fall out at the same time. In fact the average person loses about 80 hairs a day.

Hair loss, thinning and other issues happen when the growth cycle is disrupted. This can be caused by conditions such as metabolic imbalances, illness or poor diet.  For example a month or so after dieting or a high fever you can experience telogen effluvium or diffuse hair fall.

The anagen phase is reduced and numerous hairs start the telogen phase simultaneously. And if your hair growth cycle is constantly facing adversity or not receiving proper nutrition, you could discover that hair will not grow as long as it once did. This happens when hairs are not kept in the anagen (growing) phase long enough to achieve the optimum length.

The good news is you have a great deal of power over your hair science. The right diet, exercise, and rest promote hair growth. Opt for foods high in vitamins A, B, C, and E, iron, zinc, copper, magnesium, and selenium.
For more about healthy hair see: