Hair is made up of proteins that are produced by cells within the follicle.
The hair shaft also begins here. Keratinisation is the process through
which cells mature. The cells are totally keratinised by the time the shaft
protrudes through the skin. The hair is now only made up of keratinised
protein cells, which are not live cells. Hair is composed of around 90%
keratin and 10% pigment, water and lipids.

The medulla is protected by the coarser-textured cortex, which ensures
is strength and stability. The cortex is the most densely packed section
of the hair. Pigmentation of the hair occurs as a result of melanin
deposits in the cortex; the more deposits, the darker the hair.

Hair Density
Hair density is the amount of hair strands on the head, and is measured
by counting the number of hair strands found in one square inch (2.5cm)
of scalp. Generally, the classifications of hair density are thick, medium,
and thin, and are unrelated to the texture of the hair. The average head
has approximately 2,200 strands of hair per square inch, and a total of
approximately 100,000 hairs.