Epidermal derivatives

Epidermal derivatives

1. Hair and Hair follicles

   • Keratinized structure
   • 2 Parts : hair follicle and hair shaft
   • Hair follicle= tubular invagination of epidermis and is responsible for the growth of hair
   • Hair bulb= end portion of the hair follicle
   • Follicular bulb contains stem cells that can migrate and regenerate the hair shaft.
   • Dermal papilla=vascularized connective tissue
   • Hair follicle= external and internal root sheath

2. Sebaceous glands

   • Holocrine saccular gland
   • Secretory portion of sebaceous gland lies in dermis, excretory duct opens into the hair follicle
   • Secretory portion consists of alveoli connected to excretory duct by a short ductule
   • Excretory duct lined by stratified squamous epithelium continuous with the external root sheath of the hair.
   • Oily secretion of the gland is released on the surface of the hair and the epidermis

3. Sweat gland

   • 2 types: Eccrine and Apocrine
   • Both types are tubular and release their secretion by a merocrine process
   • Eccrine sweat gland:
     • all regions of skin
     • participate in control of body temp
     • composed of 3 cell types: clear, dark, myopepithelial
   • Apocrine sweat gland:
     • occur in axilla, mons pubis, anal area, external auditory meatus and glands of Moll of the margin of the eyelids
     • Only after puberty, supplied by adrenergic nerves
     • Secretory portion located in dermis or hypodermis