Know what is inside your hair

Hair Biology

Hair, the most important part of good looks, is a complicated structure with several parts making up its anatomy. Not only for good looks, hairs are also responsible for sensory transmission. Moreover they are completely renewable without causing any scarring to the skin. Let’s see what is inside the hair which makes hair such a versatile entity. Not just that, plenty of hair cosmetics and hair care products are around these days such as hair loss shampoo, hair growth shampoo etc., but all of them are not good. To know just the right hair cosmetics, you need to know about your hair.

Hairs take birth in a stocking-like structure called a hair follicle. It is the factory which produces hair throughout one’s life. The average human head has about 100,000 hair follicles.

Once the number of follicles is decided at fetal stage, it doesn’t get added up ever during one’s life time. With increasing age, the density of follicles goes down. These follicles, unless affected by certain factors such as genetics, hormones, medicine etc. keep one’s head full of hair. The hair fiber is made of a protein called keratin and consists of three layers:
Hair follicle, the hair producing factory consists of following components:


The transparent inner root sheath (IRS) clings to the hair shaft. IRS supports the hair shaft up to the level of the isthmus (see below), at which it breaks down and exfoliates in the infundibular space (see below.)


The outer root sheath (ORS) is coated over the IRS from the start of the hair bulb (thinnest at this level) to the entrance of the sebaceous gland duct.


It surrounds the vitreous layer. It is the outermost layer of the hair follicle. It is made of thickened collagen bundles that coat the entire hair follicle. The root sheath is below papillary dermis and above dermal papilla.


The suprabulb region starts from hair bulb and ends at isthmus. It has components of the hair shaft, IRS, ORS, vitreous layer, and the fibrous root sheath.


Isthmus starts from the attachment of the erector pili muscle (bulge region) and extends into the entrance of the sebaceous gland duct. At this level, the IRS undergoes fragmentation and exfoliation while ORS gets fully keratinized.


The infundibulum rests above the entry of the sebaceous duct and constitutes the upper portion of the hair follicle. Infundibulum is surrounded by surface epidermis. At the base of a hair follicle is the hair root. The most important part of hair root is a projection termed the dermal papilla. This part nourishes the hair through capillaries, or tiny blood vessels, in the papilla.

Moreover, the dermal papilla acts as a regulator for hair growth by its interaction with male hormones and androgens. If a person’s genetic coding is such that it encourages the baldness, it is this part which is affected first. Androgenetic alopecia occurs because genetically induced baldness involves these male hormones.

Moreover pigmented cells growing at the dermal papilla decide what would be the color of our hair because of the a chemical pigment (melanin.)

The hair root is surrounded by the Sebaceous glands and sweat glands. The sweat glands regulate the temperature of hair and body by secreting salt-water (perspiration) when it becomes too hot. The Sebaceous glands pours sebum oil which protects the hair and keeps it shiny and waterproof.