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Healthy Hair
The scalp is nothing but the skin on the head. The skin of the scalp is similar to the skin elsewhere on the human body and like the skin, consists of two layers: the dermis and the epidermis. However, large and deeper hair follicles are present on the scalp to accommodate the longer hair of the head.
The hair is composed of a protein called keratin. The chemical composition of hair is :
Carbon
: 50.56%
Hydrogen
: 6.38%
Nitrogen :
17.14%
Sulphur
: 5.00%
Oxygen
: 20.85%
The chemical composition varies with the colour of the hair. Full grown hair is divided into two parts : the root and the shaft. The rate of hair growth varies from person to person. The average growth of hair is approximately ¼ inch per month, i.e. 1/16 inch per week. The growth of hair is always greater between age of 20 and 30 and faster in summer than in winter. The growth of hair is cyclical, i.e. after a few years of growth, the hair enter a phase of inactivity, then dies and falls. A hair dies when its bulb is separated from the papilla that feeds it. The hair bulb is a thickened club-shaped structure forming the lower part of the hair root. The lower part of the hair bulb is hollowed out to fit over and cover the hair papilla. The papilla is a small cone-shaped elevation found at the bottom of the hair follicle that fits into the hair bulb. Within the papilla is a rich blood and nerve supply, which contributes to the growth and regeneration of the hair. Though the papilla, the nourishment reaches the hair bulb.
The growth of the scalp hair occurs rapidly between the ages of 15 and 30, but declines sharply between 50 and 60. scalp hair grows faster in women than in men. A certain amount of hair is shed daily. The average daily shedding is estimated to 50 to 80 hairs. Hair loss beyond this estimated average indicates some scalp or hair trouble. Eyebrow hair and eyelashes are replaced every 4 to 5 months.
The average life of a hair will range from 2 to 4 years. Factors such as sex, age, type of hair, heredity and health affect the duration of its life. The average area of a head is about 420 square inches and there is an average of 10,000 hair per square inch. The number of hair on the head vary with the colour of the hair, and the colour of hair, whether it is fair, brown or black, depends on natural pigment on its cortical cells- melanin. Melanin is produced in the pigment cells of the bulb and then passed into the cells of the cortex.
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