• Keratinocytes are the predominant
cell type in the epidermis.
• Langerhans cells form part of the
immune system and function as antigenpresenting
cells.• Merkel cells are mechanoreceptors
of neural crest origin.
• Melanocytes:
• Are neural crest derivatives
• Are usually located in the
stratum germinativum
• Produce melanin, which protects
the surrounding skin by absorbing UV
light.
• The dermis accounts for 95% of
the thickness of the skin.
• The papillary dermis is
superficial and contains more cells and finer collagen
fibres.• The reticular dermis is deeper
and contains fewer cells and coarser collagen
fibres.The dermis is composed of the following.
Collagen fibres• These fibres are produced by
fibroblasts.
• They are responsible for much of
the strength of the skin.
• The normal ratio of type 1 to
type 3 collagen is 5 : 1.
Elastin fibres• These are secreted by
fibroblasts.
• They are responsible for the
elastic recoil of the skin.
Ground substance• This consists of the
glycosaminoglycans (GAGs), hyaluronic acid, dermatan
sulfate and chondroitin sulfate.• GAGs are secreted by fibroblasts
and become ground substance when hydrated.
Vascular plexus
• This separates the denser
reticular dermis from the overlying papillary dermis.
