Page 76 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Anagen Growth
Catagen Regression
Telogen Resting
Exogen Shedding
Anagen Phase
During anagen the follicle enlarges and returns to its original shape. The anagen stage can be sub-divided on to six distinct phases – during stages 1 to 5, the stem cells proliferate and migrate down the follicle to enclose the dermal papilla. They then begin to grow cells for the hair shaft and the inner root sheath. Melanocytes in the hair matrix produce new melanin cells which populate the growing hair shaft. In stage 6 the hair bulb and papilla are fully grown and the new hair appears above the skin surface. A number of regulatory proteins are thought to be required for the anagen phase including vascular growth factor (VEGF), fibroblast growth fact (FGF), hepatic growth factor (HGF) and insulin-like growth factor (IGF-1).
Figure 26 – The hair growth cycle
Towards the end of the anagen stage thinning and lightening of the pigment at the base of the hair shaft takes pace, and melanin production stops. Melanocytes reabsorb their dendrites. During anagen the follicle receives its nourishment through the dermal papilla.
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 germ cells during this phase.
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