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 an on-line reference by Dr. John Gray,
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Page 12 -- HAIR

World of Hair Table of Contents - Hair Care and Hair Products Research Hair Care Research - Introduction to Hair - P&G Hair Products Hair Structure - P&G hair care research, a scientific companion Structure of hair bulb - mid-follicle - hair shaft Cosmetic Hair Treatments Hair Care Index

Hair structure
In this section we look at what hair is made of, how it is able to grow as long as it does, and what helps it to grow.
   A hair is a specialised outgrowth of part of the skin called the epidermis. It has two distinct parts, the hair follicle and the hair shaft.

The hair follicle

A hair follicle is a tiny cup-shaped pit buried deep in the fat of the scalp. The follicle is the point from which the hair grows. It is well supplied with minute blood vessels, and the blood passing through them nourishes the growing region. The temperature around the follicle is normal body temperature, and is not affected by cold or hot weather.
    The hair of an animal like a cat or a horse grows at different rates depending on the

    structure of hair follicle in growing phase

Structure of hair follicle while it is in the growing phase [Source Color Atlas of Differential Diagnosis of Hair Loss David A. Whiting and F. Lester Howsden, Fairfield, NJ: Canfield Publishing Inc.]

 
structure of hair bulb
The structure of the hair bulb
amount of natural light, which varies according to the time of year: it grows more quickly in winter when the days are short.
Human hair probably behaves in the same way, growing a little faster in winter than in summer.
The hair follicle can be divided into two regions.

The hair bulb
The hair bulb lies inside the hair follicle. It is a structure of actively growing cells, which eventually produce the long fine cylinder of a hair.
   New cells are continuously produced in the lower part of the bulb. As they grow and develop they steadily push the
previously formed cells upwards. When the cells reach the upper part of the bulb they begin to change, and they arrange
themselves into six cylindrical layers, one inside the other. The inner three layers of cells become the actual hair. The outer three layers become the lining of the hair follicle - the inner root sheath.
  Special cells in the hair bulb produce the pigment that colors the hair. The pigment is called melanin, and these cells are known as melanocytes. As the developing hair moves upwards in the follicle the melanin is carried upwards in the inner part of the hair.
World of Hair Table of Contents - Hair Care and Hair Products Research Hair Care Research - Introduction to Hair - P&G Hair Products Hair Structure - P&G hair care research, a scientific companion Structure of hair bulb - mid-follicle - hair shaft Cosmetic Hair Treatments hair care index