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Structure of Hair


Parts of Hair-



The anagen hair or the active hair follicle is divided into 3 parts—


The Upper part or Infundibulum: It is funnel shaped and extends from the epidermis to the opening of the sebaceous gland.


The Middle part or the Isthmus: Lies between the duct and the attachment of arrector pilorum muscle.


The Lower part or the Inferior segment: It is divided into stem and the bulb. It has rich network of capillaries and nerves.


Stem is the part of the follicle above keratogenous zone upto the insertion of the arector pilorum. Bulb contains follicular papilla at the centre consisting of fibrocytes, thin collagen bundles and the ground substance that is continuous with the surrounding dermis.


The hair bulb has 6 inner layers- from inward out— Medulla, Cortex, Cuticle of inner root sheath, Huxley’s layer, Henley’s layer, Outer root sheath.

http://innoson.us/pic/structure_of_the_hair_follicle.jpg http://www.pgbeautygroomingscience.com/assets/images/twoh/Chapter%201/Hair%20Structure%204.jpg


Hair composition

Hair is composed of 85% keratin, 7.5 %water, 3% lipids, 2% pigment and 2% trace elements like Aluminium, Chromium, Calcium, Copper, Iron, Manganese, Magnesium, Phosphorus and Zinc of which zinc is present in high concentration. Hair is formed of hard keratin with high sulfur content that is responsible for its extra tensile strength.

Hair keratin is composed of 18 amino acids.


Hair Types

According to the thickness of the shaft, hair can be classified into:

  • Vellus (fleece): They are thin, short, unmedullated and unpigmented. They   cover most of the body surface.
  • Terminal: They are dark, thick, medullated, pigmented and long.They cover scalp, beard, moustache, axilla and pubis.
  • Lanugo (wool like): They are those that cover the fetal skin and are shed at the age of 7-9 months. They are thin, unmedullated, light coloured but are longer than vellus hair.


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