Skin Structure & Function Flashcards
What are the three layers of the skin?
Epidermis
Dermis
Subcutis
How is the epidermis connected to the dermis?
Basement membrane zone (inherited or autoimmune diseases affecting the BMZ can lead to blistering of the skin and mucous membranes)
What epithelial subtype is the epidermis?
Stratified squamous epithelium
What is the predominant cell type in the epidermis? Where do they originate from?
Keratinocytes (keratin synthesising cells)
Originate from proliferating basal layer.
Differentiate and migrate out to the surface (around 30 days, faster in psoriasis)
Synthesise keratin filaments of cytoskeleton and desmosomal proteins (cell-to-cell adhesion).
Where are epidermal lipids synthesised?
Granular layer.
Form a watertight, intracellular layer
What is filaggrin?
Expressed in outer layer of stratum corneum.
Acts as natural “moistening factor” - keeps skin hydrated.
Consequences of filaggrin deficiency?
Stratum corneum provides skins barrier function.
“Leaky” dry skin that cracks, allowing entry of allergens and pathogens.
Mutation in filaggrin is a risk factor for atopic eczema.
What do keratinocytes secrete other than keratin?
Cytokines (e.g. interleukins, IFN gamma and TNF alpha) in response to injury –> stimulates wound healing.
Antimicrobial peptides
Where is melanin produced?
Melanocytes from the basal layer - transfer UV protecting pigment to keratinocytes
What is the dermis?
Tough matrix of collagen and elastin fibres surrounded by gel like substance. Contains cells (e.g. fibroblasts, mast cells, lymphocytes, and dendritic cells), blood and lymphatics, nerves, muscles and appendages.
What is the papillary dermis?
Upper part.
Finger like projections with terminal capillary networks
What is the reticular dermis?
Lower part.
Thicker and denser cf. papillary dermis.
