A summary of the major events of the hair cycle, and known …

• Introduction
• Morphogenesis
• Anagen
• Anagen-to-catagen transition
• Catagen
• Telogen
• The follicle stem cell compartment
• Telogen-to-anagen transition
• References
• Figure

Biology Articles » Anatomy & Physiology » The hair cycle » Catagen

Catagen

- The hair cycle

Catagen is the dynamic transition between anagen and telogen(Muller-Rover et al., 2001). During catagen, the lower `cycling'portion of each hair follicle regresses entirely in a processthat includes apoptosis of epithelial cells in the bulb andouter root sheath (ORS), the outermost epithelial layer (Lindneret al., 1997). HS differentiation ceases, and the bottom ofthe HS seals off into a rounded structure called a club, whichmoves upward until it reaches the permanent, non-cycling upperfollicle, where it remains anchored during telogen. As the lowerfollicle recedes, a temporary structure forms – the epithelialstrand – which is unique to catagen. This connects theDP to the upper part of the hair follicle, contains many apoptoticcells and is completely eliminated by the time the DP reachesthe cells that surround the remnant club hair.