The catagen phase, also known as the transitional phase, marks the end of the active growth phase (anagen) of hair. This phase is relatively short, lasting about 2-3 weeks. During this time, the hair follicle undergoes a series of changes:
Involution: The lower part of the hair follicle shrinks and detaches from the dermal papilla. Cell Death: Apoptosis (programmed cell death) occurs in the hair matrix cells. Formation of Club Hair: The hair transforms into a club hair, which is non-growing and will eventually be shed.
