Page 155 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
The anagen phase can last between a few weeks up to a few years (scalp). Light-based therapies appear to destroy follicles ONLY during this phase. This appears to be due to the availability of the maximum number of stem cells during this phase.
Light-based treatment of hair follicles will only work effectively in the anagen phase – but it becomes increasingly difficult as the bulb descends towards the sub-cutis (Figure 87).
Phase
Progress
A1
Dermal mesenchymal cells condense close to the base of the telogen follicle dermal papilla (DP). Germ cells undergo a rapid period of mitotic activity, resulting in activation of the hair germ. Melanogenesis begins and the bulge stem cells proliferate rapidly. (Uno, Suen et.al.)
A2
A short period when the germ cells start to grow around the dermal papilla (DP). The first stages of keratinisation begin and the IRS starts to grow. The bulb and DP begin to descend into the dermis at a rate of around 0.25 mm per day. (van Vlimmeren et.al.)
A3
Most of the development of the follicle occurs in this stage. The follicle will eventually reach its full length in this phase – typically around three times the length of the telogen size. By this point the bulb and matrix are fully formed – these are mainly responsible for the growth of the hair shaft. The DP cavity becomes constricted at the base while melanin granules become aligned with the DP. At the end of phase 3, the base of the follicle structure is located within the sub-cutis. The duration of phase three depends on the thickness of the dermis. Blood vessels begin to connect to the bulb and growth and melanin pigmentation of the hair shaft begin. (Chase, Uno)
In the upper bulb region, a cone begins to form. This will become the cortex and medulla of the hair shaft containing melanin granules. The inner root sheath merges into the wall of the telogen follicle. At this point, a club hair may remain in the telogen follicle, occupying the pilary canal where the newly formed hair shaft is growing. The club hair may be shed at this time (exogen). Growth of the hair shaft and pigmentation continue (Uno). By this point, the follicle structure is fully formed.
The tip of the hair shaft now breaks through the top of the internal sheath, which is about level with the epidermis. The hair now becomes visible for the first time. The follicle is fully formed by the end of stage 5. (Chase)
The hair shaft continues to grow through the epidermis for the duration of the anagen phase, at a rate of around 0.3 to 0.45 mm/day, depending on the body site and ethnicity. (Bouabbache et.al.)
A4
A5
A6
________________________________________________________________________ 155 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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