Hair is the crowning glory of man. There are approximately 90,000 to 150,000 strands of hair on your head at any one point of time. Hair can be colored, blown, cut, curled, crimped, and bleached. It is the most important aspect of our personality. Almost sixty percent of our looks are attributed to our hairstyle. It is essential for us to know all about hair growth and structure in order to cultivate a health, well nourished mane. There are various types of hair such as dry hair, normal hair, oily hair and combination hair.
Hair Growth and structure:
Hair below the surface of the skin rests in a bag-like structure called the follicle. Most hair follicles contain sebaceous glands which secrete oil into the follicle. The oil flows over the hair, lubricates it and keeps it supple. A muscle known as arrector pili is attached to most hair follicles. When we feel frightened or are cold, this muscle contracts, causing the hair to stand on end and forms little bumps around the hair known as goose pimples.
The root of the hair is the lower most part of the hair that enlarges at the end into a hair bulb. Hair develops from the cells of the bulb which divide rapidly. A structure called the papilla, containing connective tissue and blood vessels that supply the blood necessary for the rapidly growing cells of the hair, projects into the hair bulb at the base of the follicle. The cells of the hair move upwards as new cells begin to form beneath. As this move upwards, they are cut off from nourishment and they start to form a hard protein called keratin. This process is called keratinization. The part of the hair where keratinization has occurred is called the shaft. The shaft comprises of three layers of cells — the outer layer called the cuticle which has flattened cells known as cuticular cells. Beneath this lies the cortex, which contains melanin, a pigment that determines the color of hair. Hair also contains a yellow-red pigment that is most visible in people whose hair has little melanin. When the pigment no longer forms the hair gradually becomes gray or white as one grows older. The core of the shaft is called the medulla. The texture of the hair depends on the shape of the hair. Straight hair has a round shape and wavy, curly hair is flat. The flattest hair is the waviest and curliest.
Growth of hair:
Hair growth and structure go hand in hand. The growth of hair in the follicles occurs in three cycles. The follicle goes through a growth phase or the anagen phase, during which the cells of the hair bulb actively divide and produce the growing hair. The hair follicle then goes into the catagen phase or the transitional phase of activity. The cells stop dividing and the hair develops a brush like zone known as club hair. This stage is them followed by the telogen phase or the resting phase of the hair cycle. The club hair remains within the shortened follicle until a new anagen follicle develops. The newly formed hair shaft dislodges the club hair, leading to normal hair loss. Thus, while combing, we find that hair has dislodged during the telogen phase. This is a natural phenomenon. The average period of growth of hair is three to four hours and the resting phase lasts for approximately three months. Normally, 80 to 90 per cent f all scalp hair is in the anagen phase at any one point of time. Scalp hair grows less than 13 mm per month. Factors such as diet, exercise and general health also affect the growth of hair. Hair grows faster in summers than in any other season. Generally, the distribution of the growth of hair in men and women is under complex genetic and hormonal control. If produced in excess the male hormone androgen can result in male pattern baldness. When follicles on the scalp die and no longer produce new hair, baldness occurs.