A closer look at hair. (Gleams & Notions).
Today, hair still serves as protection. A thick head of hair can cushion a blow to the head. Eyelashes are very sensitive and cause a reflex shutting of the eyelids whenever a foreign object comes near.
Eyebrows keep water, sweat and oils from running into eyes. Both the ears and nose have special hairs which line the passages of these organs and catch particles of dust to prevent them from entry. Finally, haw protects the body from friction caused by muscular movement and clothing. For example, armpit hair prevents irritation caused by the rubbing of the arms and body at this juncture. It also assists in the evaporation of sweat from this area by increasing the surface air contact with sweat droplets.
How Hair Grows
Hair growth is caused by the development of small pockets in the skin called follicles. Nearly the entire surface of the skin is covered with them. Most follicles remain inactive and never produce hair. Conversely some are very active, especially on the scalp. Other follicles may only produce hair after puberty. Still others will produce hair abnormally, such as excessive facial hair on women, which may be caused by a glandular disturbance.
Hair starts growing at the base of the follicle (see diagram) which is about a sixth of an inch below the skin's surface in adults. The hair shaft surrounds a small upraised nubbin of connective tissue called the dermal papilla. The papilla is shaped like a doorknob with the neck at the base being the narrowest section. The upper portion of the papilla is covered with a thin layer of epidermal cells which divide rapidly. As they are pushed upward, they create keratin. Four keratin helices twist around each other to form a protofibril. Eleven protofibrils form a microfibril which bundle together into macrofibrils and fill each hair cell. By the time the cell has moved a fiftieth of an inch upward from the dermal papilla, keratin fibers are fully formed. In other words, the hair is dead before it emerges from the skin surface.
A small muscle, the arrector pili, is attached to the wall of the follicle and to the lower layer of the epidermis. If this muscle is contracted, the hair becomes more erect or upright. At the same time, the whole follicle is raised to form what is commonly known as a "goose pimple." In order to combat the cold, the hairs create a blanket of warm, still air around the body, similar to a bird that fluffs its feathers on a cold day.
Sebaceous glands emit a natural oil (sebum). The glands can be found everywhere on the skin except the palms, soles and between toes and fingers. Sebum forms a thin film over skin and hair surfaces. It probably helps to reduce moisture loss, protects against absorption of foreign substances and helps shield the skin from infections. Excess sebum production and bacterial infection of the follicule opening may result in acne vulgaris.
The 100,000 to 150,000 hair follicles go through their growth cycle completely independent of one another. If the follicles were synchronized, our hair would all fall out at the same time and we would shed like some animals do.
HARVEY FISHMAN HAS A CONSULTING FIRM AT 34 CHICASAW DRIVE, OAKLAND, NJ 07436, HRFISHMAN@MSN.COM, SPECIALIZING IN COSMETIC FORMULATIONS AND NEW PRODUCT IDEAS, OFFERING TESTED FINISHED PRODUCTS. HE HAS MORE THAN 30 YEARS OF EXPERIENCE AND HAS BEEN DIRECTOR OF RESEARCH AT BONAT, NESTLE LEMUR AND TURNER HALL. HE WELCOMES DESCRIPTIVE LITERATURE FROM SUPPLIERS AND BENCH CHEMISTS AND OTHERS IN THE FIELD.
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|Author:||Fishman, Harvey M.|
|Publication:||Household & Personal Products Industry|
|Date:||Jun 1, 2002|
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