Skin Anatomy Flashcards
What are the functions of skin?
thermoregulation, sensation, moisture balance, barrier to disease, control of bacterial bioburden
Skin loss/wounding classifications: erosion
loss of epidermis only
Skin loss/wounding classifications: partial thickness
loss of epidermis and part of the dermis
Skin loss/wounding classifications: full thickness
loss of all dermis and into subcutaneous tissue
Skin evaluation - what to look for
Color (yellow for jaundice, blue for cyanosis); Moisture (dry for aging, clammy for stress); Temperature (cold for vascular insufficiency, hot for infection); Texture (smooth and supple for hyperthyroidism); Turgor (increased tenting in dehydration)
Primary cell in epidermis
keratinocyte (renewed every 20-30 days, form the basal, reproducing layer)
What is the blood supply like to the epidermis?
POOR! Avascular!
What are melanocytes?
found in the basal layer, responsible for skin color and produce melanin pigment in response to UV light
What is the role of keratinocytes in wound healing?
migration/proliferation, ECM production, growth factor/cytokine production, angiogenesis, matrix synthesis/regulation
Dermis structure
beneath the epidermis
Is a matrix composed of collagen (mostly Type I),elastic fibers, and ground substances such as glycosaminoglycans (GAGs) and proteoglycans
Contains
Capillaries that feed the epidermis
Hair follicles with erector muscles that cause “goose bumps”; hair follicles lined with epithelium
Eccrine (sweat) glands – allow fluid release for temp control
Exocrine (sebaceous) glands – produce sebum for lubrication
Apocrine (scent) glands
Nerve endings for heat, cold, pain, itching, pressure, vibration
Lymphatic glands – remove microbes and excess interstitial fluid, provide lymphatic drainage
What is the role of fibroblasts in healing?
migration/proliferation, ECM production, growth factor/cytokine production, angiogenesis, matrix synthesis/regulation
What factors impact collagen synthesis?
adequate oxygen supply, sufficient nutrients, cofactors (vitamins and trace metals), local wound environment
What are the functions of the dermal/epidermal junction:
mechanical support, barrier for permiability/evaporation, basal cell support
Fun facts about the dermal/epidermal junction
Note that skin appendages penetrate into the dermis
Hair follicles, especially, are lined with normal keratinocytes
No blood crosses this membrane but oxygen and nutrients diffuse into the germinal layer
When junction flattens as in aging, epidermis can slide across the dermis, leading to SKIN TEARS
Dermis layers: papillary
provides anchoring points, contains nerve endings and blood vessels
Dermis layers: reticular
consists of irregular dense connective tissue, fibrils of collagen and elastic fibers
Dermis does this!
gives the skin elasticity and extensibility
Rete Pegs
Area between the epidermis and dermis
Called the basement membrane, isolates the epidermis from the dermis
Rete pegs, downward and upward projections fit together
Irrigation of the skin - flow chart
perforating vessels > reticular plexus > papillary plexus; arterioles are joined via capillaries to the venous plexus
Cellular components of skin structure
fibroblasts - secrete collagen, receptors for estrogen, vitamin D, thyroid hormone, steroids, growth factors; mast cells - release histamine; macrophages - immunologic cells, present antigen, phagocytosis
What is wound healing orchestrated by?
carefully regulated release of cytokines
growth factors deliver signals which have which effects?
stimulation of transcription, regulation of cell entry into the cell cycle
Growth factors facts
Polypeptides produced in normal and wounded tissue that stimulate cellular migration, proliferation, and function.
Often named for the cells from which they were first derived.
Names are often misleading, because growth factors have been demonstrated to have multiple functions.
Most growth factors are extremely potent and produce significant effects in nanomolar concentrations
cytokines
Small proteins or glycoproteins secreted for the purpose of altering the function of target cells in an endocrine (uncommon), paracrine, or autocrine fashion.
What wound healing methods are NOT EBP-based and should not be used anymore?
whirlpool! H2O, SSD
EBP protocol
Go check out the slides for the flow chart
Requirements for wound/burn healing
remove bioburden > debride > reduce periwound edema > promote granulation tissue > mobilization, prevent adhesions > epithelial migration and resurfacing, remodeling
Process of wound repair - minutes
hemostasis (platelets), inflammation (master cells, neutrophiles, macrophages)
Process of wound repair - hours
fibrin clot formation, vasoactive mediator release, cytokine and growth factor release; platelet-activating mediator release, vasoactive and chemotactic mediator release; chemotaxis, inflammation, killing and phagocytosing, wound debridement
Process of wound repair - days
skin resurfacing (keratinocytes), dermal restoration (endothelial cells, fibroblasts
Process of wound repair - weeks/months
epidermis maturation, wound contraction, apoptosis and scar maturation
additional considerations just for burns
endothelial necrosis, depletion of growth factors
predictor of burn progression
level of endothelial necrosis at 1 hour
proliferation: fibroplasia
injury > stimulation of macrophage & platelet derived cytokines & growth factors > chemo-attraction of fibroblasts to the inflammatory site > fibroblasts which are in G0 phase > replicate and proliferate > components of ECM
