Page 5 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Germ/Stem cells
All follicles have germ/stem cells which stimulate the anagen, growth
phase of the follicle’s cycle. These are only active during the anagen phase and then remain quiescent inside the bulge for the rest of the growth cycle.
Hair matrix
This is the region where matrix keratinocytes grow the hair shaft. Melanocytes are located here which provide the hair with its colour.
Melanin
Melanin is the substance which is formed by the melanocytes and gives the hair (and skin) its colour. The melanin is mostly found inside the hair shaft and is the target chromophore for all photothermal treatments with lasers and IPLs.
Hair bulb
This is located at the inferior (lowest) part of the follicle. The bulb
contains the follicular matrix surrounding the sides and top of the dermal papilla, plus some of the target melanin and stem cells. The bulb consists of the DP, mucopolysaccharide-rich stroma, nerve fibres and a single capillary loop.
Dermal papilla
The DP is the source of various growth factors which are important in the development of the follicle and hair haft, including melanogenesis. The capillaries which feed the follicle with blood are located in the dermal papilla.
Isthmus
The isthmus is the portion between the sebaceous gland opening and the stem cell bulge.
Infundibulum
The infundibulum is the upper portion of the follicle which extends from the surface down to the opening of the sebaceous gland.
Inner root sheath
(IRS)
The IRS is formed of three layers of cells which shapes the hair shaft
as it grows.
Outer root sheath (ORS)
The ORS encases the hair shaft and IRS and extends from the bulb up to the epidermis.
Table 1 – General terms and expressions used when discussing hair
________________________________________________________________________ 5 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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