Page 72 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Introduction – The Hair Follicle
The follicle is a downward tubular extension of the epidermis of the skin. Hair follicles, together with the sebaceous gland, form the pilosebaceous system.
Hair has two distinct structures – the follicle which is the living part, and the hair shaft which is non-living.
Attached to the follicle below the sebaceous gland is the arrector pili muscle. It is the contraction of this muscle which causes the hair to stand on end – so giving the ‘goose pimple’ effect. Hair is composed of columns of dead keratin cells. We are typically born with around 5 million hairs, with up to 150,000 of them on the scalp.
The hair follicle consists of the following structures: • Medulla
• Inner root sheath
• Outer root sheath
• Dermal papilla
The outer root sheath grows around the inner root sheath and provides structural support. At the sebaceous gland this tissue merges into the epidermis (it becomes stratum granulosum and stratum corneum) and contains melanin, from the hair matrix. Between one third and one half of the way down the follicle, the outer root sheath contains the germ cell bulge, where these cells reside. The bulge is located close to the insertion point of the arrector muscle. Small nerve fibres form a circular layer around the bulge including free nerve endings. These are triggered by heat and give rise to much of the pain normally felt during laser/IPL treatments.
These are the cells which must be thermally denatured (‘cooked’) if a successful treatment is to be achieved.
________________________________________________________________________ 72 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022
The medulla is the core of the hair – it is made up of layers of keratin cells which are formed by proliferating cells in the hair matrix at the base of the follicle. Very thin hairs don’t have a medulla.
The inner root sheath grows from the base of the follicle up to the level of the sebaceous gland. Beyond this level, the hair grows through the follicular hair canal.