Hair originates from a hair follicle -- a structure about 4 - 5 mm. deep in the skin.
Hair follicles connect to the body through the dermal papilla. Blood vessels and lymphatic vessels connect with the dermal papilla and send all important nutrients, hormones, etc. to the hair follicle for building hair.
The hair follicular unit is composed of 1 - 3 hairs, a sebaceous gland (produces oil), and an apocrine gland (produces odor).

Hair grows out from the skin as a group of 1 - 3 hairs and occasionally 4 hairs. When we get older, the amount of hair in each group declines from 3 to 2 to 1 and the diameter of the hair is also smaller with aging.


Hair Density
Humans have roughly 1 follicular unit / square mm. of scalp.
*about 2 hairs / unit = 200 hairs / sq. centimeter
*100,000 hairs on scalp = 500 sq. centimeters of scalp


Hairline Shape
In normal males and females with no baldness or receding of hairline, the hairline shape is as follows:

Hair Direction
The normal direction of the hair is from the occiput to the nose as a whorl from the back. Some still have remnants of vellus hair left on the border of the hairline.

Hair Cycle
Each unit of hair grows and rests in cycles. The growing phase (anagen) lasts about 3 - 5 years. The resting phase (telogen, catagen) lasts about 3 - 6 months.

At the catagen and telogen phases, the hair root will become club hair (dumbell shaped hair) and ready to fall off. If we rub or massage our head or comb our hair, club hair will fall off. This is a normal physiologic phenonema. Each day approximately 100 hairs will fall off in normal men.

Hair Synthesis
Hair stem cells (progeniter or pluripotential stem cells) are located at the orifice of the sebaceous gland and the insertion of irrector pilli muscle (bulge region). Stem cells will produce daughter cells at each cycle of hair growth.

Daughter cells will differentiate to become full follicular units and produce hair. At the end of the hair matrix and papilla interaction, each hair cell becomes a dead cell and piles up through the hair canal to become a hair shaft growing out of the skin.

Hair synthesis requires the highest metabolic rate in the body. So in the event that anything interrupts with this process, hair will stop growing and fall out. Examples: in chemotherapy for cancer, shock stage, after typhoid fever, after delivery of a baby, etc.

Causes BALDNESS

What Causes BALDNESS?

Common baldness or androgenic alopecia is caused by:

1. Genetics: a baldness gene in chromosomes is a must for baldness. Baldness is hereditary and sometimes occurs
   even without a family history of it; baldness can happen because of mutation of genes.
2. Male Hormones: testosterone and dihydrotestosterone (DHT).
3. Aging and degenerating factors.

Progress of Baldness (androgenization)

ANCIENT THAI CLASSIFICATION OF BALDNESS

Chadowteepang Cheekduanfard Dongchangkam Ngamtepo

Rajklungklao Ranggapuepeek Tungmahlong

Medicines with some Effects on Hair Roots

1. MINOXIDIL: increases the size of the hair by stimulating the blood supply to the hair root, but it also will stimulate unwanted hair on the face and body.

2. FINASTERIDE,DUTASTERIDE: a drug acting with the anti-male hormone (DHT) by stopping the enzyme 5 alpha reductase. As a result, any miniature hair on the scalp can grow longer. It lessens hairloss but Finesteride can cause loss of sexual desire and inferlity.