What you really should know about your hair type, hair growth, and hair distribution

There are about 100,000 hair on your scalp. The hair on your scalp and eyebrows is classified as terminal hair although the scalp hair is often coarser and longer than eyebrow hair.

Hair growth and density are influenced by factors such as nutrition and hormones. Poor nutrition usually equates to retarded hair growth. On the other hand, conditions that increase the local dermal blood flow such as chronic physical irritation or inflammation may enhance local hair growth. Perhaps that's why braiding the hair nightly promotes growth. Although braiding the hair too tightly can cause scalp damage and therefore alopecia. Testosterone also encourages hair growth, and when male hormones are present in large amounts, terminal hair growth is luxuriant.

In women, small amounts of androgens are normally produced by both the ovaries and the adrenal glands. Excessive hairiness (hirsutism) with other signs of masculinization may be manifestations of an adrenal gland tumor that secretes abnormally large amounts of androgens. This tumor can be surgically removed.

On an average, hair grows about 2mm per week. Each follicle goes through growth cycles. In each cycle, an active growth phase is followed by a resting phase, when the matrix is inactive and the follicle base and hair bulb atrophy somewhat. After the resting phase, the matrix proliferates again and forms a new hair to replace the old one that has fallen out or will be pushed out by the new hair.

Don't panic if you are reading this because your hair is not growing to your desired length. And this is why you should not panic. The life span of the hair varies. The follicles of the scalp remain active for about for four years before becoming inactive for a few months (so you have four years to grow a newly sprouted hair to the desired length. Also remember that hair shafts sprout at different times. So, you will always have hair long enough on your head when you shed one whose time has expired). Because only a small percent of your hair follicles are in the shedding phase at any one time, you lose an average of 90 scalp hair daily (lets do the math 90/100,000=.09% daily and don't forget about new growth). To help you better understand why you should not be losing hair for this, not that the follicles of the eyebrow hair remains active for only three to four months which explains why your eyebrows are never as long as your hair.

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