Structure of Hair

Jennifer Slone


Cell division in the hair matrix produces the cells that form the major structures of the hair fiber and the inner root sheath.
Packed dead cells surround these structures and are known as the cuticular layers of the hair.
In the center of the structures lies the medullary canal, which is actually apart of the excretory system and houses any foreign debris, heavy metals, synthetics and medications that are thrown off by the body and eventually released through the canal.


Cuticle - The outermost layer of the hair shaft.
Scales - Covers the hair shaft.
Cortex - The middle layer in the hair shaft and holds the hair's pigment.
Cortical fusi - Small spaces within the hair shaft filled with either water or air.
Medulla - Innermost layer of the hair shaft; the central axis surrounded by the cortex.

Hair Muscles

When the body is too cold, the arrector pili muscles found attached to hair follicles stand up, causing the hair in these follicles to do the same.
(This is the muscle that makes hair stand erect and produces goose bumps in your skin when you are cold.)

3 Scale types

Base - Medulla

The medulla is a tube in the very center of the hair fiber.
The medulla is where nerve fibers and blood vessels penetrate through small gaps in the base of the hair capsule and invade the DP area.

5 Medulla Types

Facts About Hair

The average number of hairs on the scalp of an adult is about 100,000.
The average daily loss of hair on the scalp is between sixty and one hundred hairs.
The bigger the DP, the more cells it has, then the thick the hair fiber that the hair follicle produces.