The human hair fiber can be described as a long, thin, cylindrical, and flexible shaft consisting of a core covered by relatively thin and flat, but circumferentially curved, overlapping cuticle cells. The core, or cortex, is composed of elongated, keratinized cells aligned, or slightly inclined with the direction of the longitudinal fiber axis, and often contains a centrally located, strand of highly vacuolated hardened cell remnants known as medulla cells (Orwin, 1979a).
Cortical cell types and intermediate filament arrangements correlate with fiber curvature in Japanese human hair Journal of Structural Biology Volume 166, Issue 1, April 2009, Pages 46-58 Journal of Structural Biology https://www.sciencedirect.com/science/article/abs/pii/S1047847708002980
細胞からできているといっても、ケラチンを多量に産生して一生を終えた細胞ということだと思います。
Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells.
