7.3.1: Hair Fiber Production

  • The dermal papilla contains undifferentiated cells (cells that are not fully developed or specialized) that multiply and proliferate into hair fiber cells.  As the cells multiply the constant stream of production pushes the cells upwards towards the skin surface. As they move up the hair follicle they begin to differentiate into particular hair cell types.
  • The cortex cells are formed by squeezing the cells from the papilla together into layers and changing them from a round-shape into a flattened appearance. At this stage the melanin pigment is incorporated into the cortex cells. These cortex cells become keratinized, harden, and die. The keratinized cells are continually pushed upwards, away from the hair bulb region, as new cells are produced in the dermal papilla.
  • Some hair strands have a central area of cells that are loosely organized and not packed together. This area of the hair fiber is called the medulla.
  • Around the outside of hair fiber is a cuticle which is made up of more keratinized cells that are arranged differently to cortex cells. As the cuticle cells are produced, they lay over the cortex cells and flatten into an overlapping roof tile fashion.  As with cortex cells, when they keratinize the cell hardens and dies.
  • The cells in the bulb divide every 23 to 72 hours, faster than any other cells in the body.