Introduction air
is composed of keratin, the same protein that makes up nails and the
outer layer of our skin. Hair on the scalp can be divided into two parts, the root and shaft. The root
part of hair is in a cavity of the skin (epidermis) of the scalp.
The hair root is surrounded by a pouch like structure called hair
follicle. The base of the hair root is in the shape of a bulb. At the
base of the hair follicle are sensory nerve fibers that wrap around each
hair bulb. Bending or touching hair stimulates the nerve endings and
tells the body that the hair has been moved. This is one of the main
functions of hair..... to act as a sensitive touch receptor.
The cells in the center of the bulb divide. The newly divided hair cells
push the previous cells up. The cells which move upwards die slowly
forming hard hair shaft.
The
hair shaft has 3 layers:
1. Cuticle is the
outer layers and protects the inner layers. It is transparent. Healthy
cuticle gives a shiny appearance for hair and unhealthy cuticle gives
lifeless look
2. Medulla is the
innermost layer composed of large cells.
3. Cortex is the
layer between cuticle and medulla. This contains pigment and keratin.
Cortex determines the bulk and
strength of hair.
The hair follicle contains
oil secreting sebaceous glands which can make the hair shiny. The oil
gland helps remove old skin cells, keeps the skin lubricated, and
prevents drying of tissues. Stress and illness usually diminish
secretion of oil and can make hair dull and lifeless looking.
Each hair on our scalp grows
approximately at the rate of 1 centimeter per month. This growth
continues on average for about 3 years. When the hair attains full
growth it rests for about 3 months and then falls out.
A new hair starts
growing in its place. Thus at any given point of time around 15 percent of the
total hair on our scalp is in a resting phase and 85 percent of the hair
is in growth phase.
As a part of this hair growth cycle it
is normal to lose 80 to 100 hairs a day.
Over time the follicle can shrink
causing the hair to become shorter and finer. Ordinarily, the hair
should grow back but in men who are balding the very small follicle
ceases to grow any hair. The cause of baldness is not completely
understood. It is thought to be related to the genes and male sex
hormones. See a topic from the Index on left hand side of this page for
more specific details.
Hair Shape
The
natural curl of a hair is normally determined by it's
cross-sectional shape. Hair that is circular is straight. Hair
that is flattened and/or elliptical is curly or kinky. The
more circular the cross section of the shaft is, the
straighter it is. The more elliptical, the curlier or kinkier
the hair. The shape also determines the amount of shine the
hair has. Straighter hair is shinier because sebum from the
sebaceous gland can travel down the hair more easily. The
kinkier the hair, the more difficulty the sebum has traveling
down the hair, therefore the more dry or dull it looks.
itsabouthairloss.com
IMPORTANT: We are not connected to and do not endorse any of the companies advertising on this site and have no
preference for any one company over another. When you click an external
link you
will be leaving this site and our disclaimer regarding this
applies. We use the Google Adsense program and other affiliate links only
to raise revenue to fund the existence of this webpage
itsaboutHairLoss.com
The
hair shaft has 3 layers: