HairMorphology and Structure of

Human Hair

- Hair consists of dead cells which are extruded from the base of the follicle

- Hair consist of two parts; the shaft, the root or follicle

The hair is formed by cells of the dermal papilla at the base of the follicle.

Follicles are formed during the growth of the foetus, no new follicles are formed post natally.

The major function of hair is thermal insulation.

On S.E. Microscope, the hair shaft is seen to consist of three regions. The cuticle – the outer region –

encircles the cortex, and is made of 5 to 15 overlapping layers. Externally is seen as a series of uneven edges, which can be forced outwards by combing or friction. There are gaps between these layers, permitting small molecules to enter or leave the cortex.

On S.E. Microscope, the hair shaft is seen to consist of three regions.

The cortex – the middle region – which has a fibrous appearance, long strands of fibers run along the length of the hair, interweaving so as to form a structure of great strength and elasticity.

The medulla – a central canal. The cells are nucleated near the papilla, but the cell contents are lost they progress upwards. Many hairs have no medulla.

Morphologically, there are three types of hair: Vellus : are short, fine, soft, usually non

pigmented and unmedullated Terminal : are large, darkly pigmented and

often medullated90% of the hairs on the chest, trunk,

shoulders, legs and arms of men are terminal, only 45% on women.

Intermediate : occur on the scalp, their morphology falls between those of terminal and vellus and they are medullated and contain moderate amount of pigment.

Cyclic Activity of Hair

Anagen phase: The hair grows at a rate of about 1cm/ month, during which the old hair is shed and new growth begins.

Of 100,000 – 150,000 scalp hairs on human adult, regardless of sex, 90% are in the anagen phase

Catagen phase: 5% resting phase Telogen Phase: 5%

Chemical Composition of Human Hair

Protein (keratin) 65-95%, depending on its moisture content

- keratin is a biopolymer composed of 25 different amino acids, 18 in measurable amounts

Lipids Pigment and trace elements.

The extreme strength and insolubility of hair due to:

Its large cystine content The filaments of the cortex are

composed of low sulphur proteins and surrounding matrix is made up of high sulphur proteins

The cuticle cells do not contain any low sulphur proteins.

The extreme strength and insolubility of hair due to:

1- Amide links - CO – NH –2- Very long polypeptide chains3- Salt links R-NH3+ -OOCR4- Disulpide bonds which bridges two

main chains and provides a strong covalent link between them. R-S-S-R

5- Hydrogen bonding between the main chains. NH ……..OC

Hair Loss

Recently, elderly became interested in lifestyle aim to provide better diet, nutrition and drugs that not only target long life but also better quality of life.

Hair Loss

Normally, around 90% of scalp follicles are in anagen phase and 10% in catagen and telogen phases. But many factors can affect the cyclic activity of hair. These factors shorten the anagen phase, rendering terminal hair to fine vellus hair. When anagen phase shortens and telogen phase became longer, considerable percentage of hair fall out. With continuing fall of hair, baldness becomes obvious.

Hair Loss

Aging also affect the hair cycles rendering terminal hair into vellus, these changes may be explained by decreased function of hair matrix cells that produce hair, decreased blood flow causing shortage in nutrients, increased sensitivity of androgenic hormones and excess secretions of sebum that affect the healthy environment of hair growth.

Hair Loss

Other factors include malnutrition, administration of certain drugs, genetics, stress and tension may affect the cyclic activity of hair.

To treat hair loss, pharmaceuticals and cosmetic firms developed new products claimed to contain effective ingredients to address the above indirect causes of hair loss; include nutrients, blood flow promoters, androgenic inhibitors and sebum reducing agents.

 

Treatment of alopecia:

Finastride and dutastride : synthetic anti-androgen taken orally to treat pattern baldness, a form of androgenic alopecia in men. It acts by inhibiting 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT).The U.S Food and Drug Administration approved finastride to treat male pattern baldness.

Treatment of alopecia: Minoxidil : A topical agent used to

treat hair loss . Minoxidil acts as a vasodilator that increases blood supply to the follicle stimulating hair growth.

Herbal extracts have been used to treat alopecia. For example, Linum usitassimum (flax) seed extract has been used to treat male pattern baldness by inhibiting 5-alpha reductase, thus reducing levels of DHT.

Treatment of alopecia:

t-flavone from Hypericum perforatum is significantly effective in treating male-pattern and female pattern baldness. It promotes hair growth and increases the diameter of hair. t-flavone acts by suppressing the activation cascade of transforming growth factor- beta 2 (TGF-B2) , a catagen inducer secreted from the dermal papilla .

Treatment of alopecia:

6-(Benzylamino) purine; an adenine derivative is also used to promotes hair growth by converting the telogen phase in to anagen , and by stimulating DNA synthesis, allowing lengthening of hair shaft . [5]

Oral administration of soymetide-4, an immunostimulating peptide derived from soybean ,is effective in treating alopecia. [6]

Treatment of alopecia:

The liposterolic extract of Senenoa repens and hexane extract of Curcuma aeruginosa are botanically derived inhibitors of 5-alpha reductase , so can be used to treat male pattern baldness.