Hair Growth Facts

Here is a mini lesson on the structure of hair and hair growth facts. I will not go into depth but this will provide an overview for you because I do reference some of these hair growth facts through out the site.

Parts of human hair

Human hair has 2 main parts: the hair root which is below the scalp and the hair shaft which is basically the part of the hair you see.

Hair Anatomy Diagram

Selected hair structure definitions:

Follicle– tube like area that contains the hair root

Sebaceous gland– gland of the skin that secretes the oil sebum, sebum provides lubrication to the skin, hair and scalp.

Hair shaft– the part of the hair which grows out from the skin. It consists of an outer layer called a cuticle, a middle layer called the cortex, and an inner layer called the medulla (fine hair does not always have a medulla layer)

The Hair Growth Cycle

Understanding the facts about the hair growth cycle is important because there are many myths surrounding how hair grows. There are 3 phases of the hair growth cycle; these phases repeat. On average a person grows about 1/2 inch or 1.25 cm of hair each month.

Anagen Phase– new hair grows, this phase usually last from 3-5 years but can be longer for some people. When you see individuals with extremely long hair they probably have a longer than average anagen phase. About 90% of hair is in this phase at one time.

Catagen phase– the hair begins to transition into a rest phase, it is the end of the growth phase. About 1% of hair is in this phase at one time. This is the shortest phase and usually only last a couple of weeks.

Telogen phase– the hair is no longer growing and eventually sheds. About 10% of hair is in this phase at a time; it typically lasts 3-6 months.

Hair Growth Cycle Diagram

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Source Milady’s Standard Cosmetology (c) 2004