Dermis Structure Flashcards
Basic structure of the skin
-epidermis (superficial) adhered to dermis just below by the dermoepidermal junction
Dermal matrix composition
- collagen fibers + elastin fibers + ground substance
- synthesized by fibroblasts w/in dermis
Characteristics and purpose of dermoepidermal jucntion
- epidermal rete=downward projections of epidermis
- dermal papillae=upward projections of dermis
- interlocking pattern increases adherence strength and surface area (btwn epidermis and dermis) –> passage of nutrients
- pattern on hands and feet –> epidermal ridges (“fingerprints”)
General characteristics and typesof collagen
- “building block” of dermis
- provides tensile strength of skin
- three proteins arranged in alpha-helical structure
- repeated strings of Gly-X-Y (usually Gly-Pro-hydroxyproline)
- Main types: Collagen I, III, IV, VII
Type I Collagen characteristics
- > 85% of adult dermis
- major component of bone
Type III Collagen characteristics
- fetal dermis component
- reason why fetal skin forms less scars
Type IV Collagen characteristics
- high concentrations found in basement membrane zone (i.e. @ dermoepidermal jxn)
- prominent around vessels
Type VII Collagen characteristics
- found anchoring fibrils
- used to to attach epidermis to dermis
Sites of collagen synthesis and assembly
- synthesis=intracellular (fibroblasts)
- assemnly=extracellularly (w/cofactors –> vit C)
Ehlers-Danlos syndrome (EDS) characteristics
- disordered collagen production due to genetic defects
- skin hyperextensibility, joint hyperextensibility
- tissue fragility
- poor wound healing
Elastic fiber characteristics
- provide skin resiliency=ability to be distorted and return to orignal shape
- normally argyrophillic=”silver-loving” –> visible w/silver-based stains
- sun-damaged elastic fiber (e.g. in solar elastosis) =basophillic
Pseudoxanthoma elasticum (PXE) characteristics
- mutation in gene encoding multidrug resistance complex
- elastic fibers–>enlarged, tangled, and calcified
- histologically blue-purple
- “plucked-chicken” skin
Ground substance components
- gelatinous material between and amongst collagen bundles, elastic fibers, other structures of dermis
- glycosaminoglycans: hyaluronic acid and dermatan sulphate (can absorb water)
- fibronectins=”glue”
- helps facilitate nourishment of epidermis
- constantly being destroyed and renewed
Functions of cutaneous vascular system
- wound healing
- control of homeostasis: via Sucquet-Hoyer canal (smooth muscle valve) blood directed towards or away from skin
- modulation of inflammation/leukocyte trafficking: express intracellular adhesion molecules (ICAMs) that allow adherence and rolling of WBCs
Leukocytoclastic vasculitis characteristics
- immune complex formation within post-capillary venules in dermis
- often post-Strep infection
- palpable purpura
