For most parts of this exercise we will work in groups of four. Each of you should write up your own lab report based on the results your group got. Briefly describe what you did, the results you got, and your interpretation of those results. Did anything surprise you? Evaluate the experiment. Do you think this would work in the classroom? If so at what level? If not, why not? Would you make any changes in the exercise?

There are three types of hair. Vellus hairs are short, fine, soft, and non-pigmented. Terminal hairs are large and darkly pigmented. The hairs on our scalp are intermediate in pigmentation between terminal and vellus hairs. Most of the hair on men's bodies (other than their scalp) is terminal hair. Less than half of women's body hair is terminal hair. The rest is the small vellus hairs; that's why women don't appear to have as much body hair as men. Pattern baldness, more common in males than females, involves the gradual replacement of intermediate scalp hair with fine vellus hair.

Hair comes in different shapes. Elliptical or kidney-shaped hair has a "woolly" texture. It is almost always black and is found in people of African ancestry. Straight coarse long hair is the hair of the Chinese, the Mongols, and Indians of the Americas. It is usually black. Flat hair is curly or frizzy. It is found in Australian natives. Oval hair is wavy and curly or smooth and silky. It is the hair of Europeans and comes in various colors. Among those of European ancestry, blondes have a larger number of hairs (140,000) than brunettes (105,000) or redheads (90,000). The average hair of Japanese women is 1.5 times thicker than that of Caucasians.

The life of a hair goes in 3 phases. Most of the hair on our scalp is in a growing phase that lasts from two to six years. A transitional phase lasts three weeks followed by a resting phase. The resting phase ends after two to four months when the old hair is pushed out by a new hair growing from the same bulb. The hair on our eyelashes, trunk, arms and legs only grows from one to six months before the resting stage begins.

The hair on our scalp grows about a half an inch a month; beard and body hair grows at half that rate. At night hair grows slowly but it grows fastest between 10 and 11 AM. It slows for a while but speeds up again between 4 and 6 PM. Collectively you produce 1.2 inches per minute or 37 miles worth per year.

Hair loss is normal. We lose 50 to 100 hairs a day. Disease is one of the things that can interrupt the normal pattern. One to three months after someone has a high fever, severe infection, flu or major surgery she or he may lose a lot of hair. Usually the hair is replaced by new growth and the normal replacement cycle is reestablished.

During pregnancy, hair loss is slowed. Childbirth triggers many hairs of the mother to enter the resting phase of the hair cycle. Two or three months later, there will be excess hair loss. After several months the regular replacement cycle returns. When a woman stops using oral contraceptives, a similar shedding cycle is set in motion.

Various medications cause temporary hair loss. Medications to treat depression, heart problems, high blood pressure and cancer may cause temporary hair shedding. Diet is also a factor. Inadequate protein, inadequate iron or excess vitamin A may cause thinning until proper nutrition is reestablished. Thus crash diets, anorexia nervosa, and starvation can all lead to significant hair loss.

Some chemical treatments can damage hair if done too often or done incorrectly. Dyes, tints, bleaches, straighteners and permanent waves can weaken hair. Even excess shampooing, combing, brushing or braiding can break hair or cause hair loss.

Diane Witt of Worchester Mass had hair 8 1/2 feet long after letting it grow for 15 years. However, in 1959 Swami Pandarasannadhi of Madras, India was reported to have hair 26 feet in length. Hans Langseth had a 17 1/2 foot beard when he died in 1927. In 1984 a hair from Pham Thy Lan held more than 6 oz before it broke.

Our skin is spread out over 3,000 square inches The top layer, the epidermis produces layers of cells that will push out and die. These horn like cells contain no blood vessels. There are 30 layers. As the top layers get rubbed or washed off, new ones push up from the epidermis.

Our fingernails are also made up primarily of dead cells, a horn-like material called keratin. Growth takes place in the martix, the hidden part of the nail under the cuticle.   The older cells die and harden as they are pushed out.  The matrix also includes the lunula, the whitish half-moon area at the base of the nail.  Fingernails grow about 0.1 mm per day or 1-2 inches a year. Fingernails grow faster than toenails.   Nails in men grow faster than in women.  The nails on the dominant hand grow faster than on the other hand.  In the summer nails grow faster than in winter.   Shidhar Chillal of Poona, India had a total length of 158 inches of nails on his left hand. They were uncut for 35 years.

American Academy of Dermatology Nail Health pamphlet

        http://www.aad.org/pamphlets/nailhealth.html

American Academy of Dermatology Hair Loss pamphlet

        http://www.aad.org/pamphlets/hairloss.html

Boehm, David A., et al, eds. 1988. Guinness Book of World Records. New York: Bantam Books.

Leokum, Arkady. 1989. The Big Book of Tell Me Why. New York: Purlieu Press.

S & G Research: Hair Loss Research Laboratories Pamphlet

        http://www.hairloss-sg.com/pamphlet.html

The following experiment will be done on "artificial skin." We'll use gelatin to trap water much in the way that our skin holds in water.

l Boil some water.

The following experiment could be done with real hair but since it may be difficult to come up with lots of long hairs for testing, we will substitute some wool cloth instead.

Nail polish includes the following ingredients. Ground pigments give the polish its color. Nitrocellulose is a film that bonds to the nail, is glossy, and allows the nail to "breathe". A solvent dissolves the nitrocellulose and allows you to spread the polish. A plasticizer keeps the film flexible. A suspending agent keeps the pigment spread throughout the polish.

In one of the samples, the nail polish should sink into the surface because the surface is dissolved by the materials in the polish.

One of the samples should not dry very well. This is because the polish dissolves some of the material in the surface and the material combines with the solvent and prevents it from evaporating.

The third sample should form a film on the surface that can be peeled off the surface if it is thick enough.

How Strong is Your Hair?

Dry skin

• 12 pkg. unflavored gelatin
• 3 doz. small plastic cups
• Vaseline, mineral oil, glycerin, bag balm, cold cream, caladryl lotion
• medicated skin cream or other lotions
• 6 marking pens

Bleaching hair

• 18 pint jars with lids
• 3 bottles bleach (careful, poisonous and caustic)
• 3 bottles ammonia (careful, poisonous and caustic)
• 3 bottles hydrogen peroxide
• 1/8 yard wool cloth
• measuring cups
• measuring spoons

Nail polish

• 6 bottles of nail polish
• 3 rolls plastic food wrap
• 3 rolls aluminum foil
• 3 rolls wax paper

Hair strength

• 3 rolls tape
• 3 bags of screws or washers
• 6 reclosable sandwich bags with a hole punched on one side near the top
• 3 balances

  

  Saint Xavier University,  Dale Fast, Lab for Teachers

  Last updated 7 March 2001   fast@sxu.edu