Page 77 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
We suspect that that photothermal treatments may only work in the last three stages of these six!
Catagen Phase
The catagen phase typically lasts for around 2 weeks in most people. During this time the follicle enters an ‘involutionary’ phase when the follicle essentially dies! The dermal papilla separates from the matrix and the hair starts to rise in the follicle. At this time the hair held in the follicle by the cells of the inner root sheath and receives its nourishment from the follicle wall.
There are eight different stages in the catagen phase, including apoptosis (programmed cell death) of many cells throughout the follicle structure. The entire follicle essentially collapse reducing its size considerably, leaving behind an epithelial strand. This strand shortens reaching up to the insertion point of the pilo-muscle. The connection to the dermal papilla is broken leaving the follicle with no blood supply.
This phase typically lasts between 10 and 14 days.
Telogen Phase
This is known as the quiescent or resting phase, when the follicle remains inactive or dormant until stimulated into the anagen stage where the whole process is repeated.
The telogen phase is really quite boring! It is when the follicle ‘rests’ – it doesn’t really do anything interesting at all. It is the gap between catagen and the next anagen phase.
Telogen only lasts for a few weeks, with the club hair often being retained within the follicle until the new hair is produced and pushes the club hair out of the follicle. The telogen follicle is one-third to half the length of the full anagen follicle.
The telogen phase lasts between around 10 and 20 weeks, typically. During this phase the hair becomes a club hair.
Exogen Phase
During this phase the hair shed – This is thought to be an active process and, hence, it is quite independent of both the telogen and anagen phases.
Summary - the hair is a keratinised structure consisting of a number of layers. The follicle forms part of the pilo-sebaceous unit which reaches from the epidermis down to the dermal papillae situated in the dermis.
The follicle goes through a growth cycle divided into three main stages, these being :
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