Hair Morphology and Structure of Human Hair

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HairMorphology and Structure of Human Hair

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

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- 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.

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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.

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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.

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Morphologically, there are three types of hair

• Vellus are short, fine, soft, usually non
  pigmented and unmedullated
• Terminal are large, darkly pigmented and often
  medullated
• 90 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.

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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

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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.

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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.

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The extreme strength and insolubility of hair due
to

• 1- Amide links - CO NH
• 2- Very long polypeptide chains
• 3- Salt links R-NH3 -OOCR
• 4- 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

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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.

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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.

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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.

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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.
•  

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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.

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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.

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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 .

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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

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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.