Changes

==Development==

==Development==

[[image: Section of Foetal Cat Skin.jpg|thumb|250px|right|A section of foetal cat skin showing developing hair follicles. Copyright RVC2008]]

[[image: Section of Foetal Cat Skin.jpg|thumb|200px|right|A section of foetal cat skin showing developing hair follicles. Copyright RVC2008]]

Hair germs begin from an aggregation of keratinocytes in the stratum basale of the [[Skin - Anatomy & Physiology#Epidermis|epidermis]].  The initiating factor is the underlying dermal fibroblast cells.  The keratinocytes elongate, divide and relocate to the dermis.  Dermal fibroblasts then  form a dermal papilla beneath the hair germ.  This causes stimulation of the basal stem cells to up-regulate their cycle, producing cells that will keratinise and form the hair shaft.  Two swellings form on the shaft, one containing stem cells for follicle regeneration, the other becomes a sebaceous gland which will secrete sebum onto the hair shaft.

Hair germs begin from an aggregation of keratinocytes in the stratum basale of the [[Skin - Anatomy & Physiology#Epidermis|epidermis]].  The initiating factor is the underlying dermal fibroblast cells.  The keratinocytes elongate, divide and relocate to the dermis.  Dermal fibroblasts then  form a dermal papilla beneath the hair germ.  This causes stimulation of the basal stem cells to up-regulate their cycle, producing cells that will keratinise and form the hair shaft.  Two swellings form on the shaft, one containing stem cells for follicle regeneration, the other becomes a sebaceous gland which will secrete sebum onto the hair shaft.