Hair Shaft

The hair shaft (HS) is a key cornified component of the mature hair follicle (HF), situated at the center of the HF. HS is formed during upward growth and differentiation of the matrix cells and is comprised of three distinct cell layers: the innermost medulla, the cortex and the hair shaft cuticle. The number of medulla cell columns defines the thickness of the hair. In mice, zig-zag hair has a single column, guard hair – two columns, and awl hair – 2-3 columns of medulla cells.