Page 137 - TNFlipTest

Toronto Notes 2019 Morphology
Epidermal Appendages
• epidermalinorigin,canextendintothedermis;includeshair,nails,andcutaneousglands • pilosebaceousunit=hair+hairfollicle+sebaceousgland+arrectorpilimuscle
Cutaneous Glands
• sebaceousgland:partofpilosebaceousunit;producessebumwhichissecretedintothehairfolliclevia the sebaceous duct, where it covers the skin surface (protective function)
■ sebum has some antifungal properties
■ these glands cover entire skin surface and are absent only in non-hair bearing areas (e.g. palms,
soles, lips)
• apocrinesweatgland:apocrineductemptiesintohairfollicleabovesebaceousgland
■ found in axillae and perineum
■ likely a vestigial structure, functions in other species to produce scent (e.g. pheromones)
• eccrinesweatgland:notpartofpilosebaceousunit
■ found over entire skin surface except lips, nail beds, and glans penis
■ important in temperature regulation via secretion of sweat to cool skin surface
Skin Function
• protection
■ due to continuous recycling and avascularity of epidermis
■ barrier to UV radiation (melanin), mechanical/chemical insults (sensory/mechanoreceptors),
pathogens (immune cells), and dehydration (lipid rich barrier)
• thermalregulation
■ insulation to maintain body temperature in cool environments via peripheral vasoconstriction, hair, and subcutaneous adipose tissue
■ dissipation of heat in warm environments via increased activity of sweat glands and increased blood flow within dermal vascular networks
• sensation
■ touch, pain, and temperature sensation
• metabolicfunction
■ vitaminDsynthesis
■ energy storage (mainly in the form of triglycerides)
Morphology
Primary Lesions
Definition
• ade-novoinitiallesionthathasnotbeenalteredbytraumaormanipulation,andhasnotregressed
Dermatology D3
Table 1. Types of Primary Morphological Lesions
Describe a Lesion with SCALDA
Size and Surface area
Colour (e.g. hyperpigmented, hypopigmented, erythematous)
Arrangement (e.g. solitary, linear, reticulated, grouped, herpetiform)
Lesion morphology
Distribution (e.g. dermatomal, intertriginous, symmetrical/asymmetrical, follicular)
Always check hair, nails, mucous membranes and intertriginous areas
Profile
Flat Lesion
Raised Superficial Lesion
Deep Palpable (dermal or subcutaneous) lesion
Elevated Fluid-Filled Lesion
<1 cm Diameter
Macule (e.g. freckle)
Papule (e.g. wart)
Nodule (e.g. dermatofibroma)
Vesicle (e.g. HSV)
≥1 cm Diameter
Patch (e.g. vitiligo) Plaque (e.g. psoriasis) Tumour (e.g. lipoma)
Bulla (e.g. bullous pemphigoid)
Secondary Lesions
Definition
• developduringtheevolutionaryprocessofskindisease,orcreatedbymanipulation,ordueto complication of primary lesion (e.g. rubbing, scratching, infection)
• crust:driedfluid(serum,blood,orpurulentexudate)originatingfromalesion(e.g.impetigo)
• scale:excesskeratin(e.g.seborrheicdermatitis)
• lichenification:thickeningoftheskinandaccentuationofnormalskinmarkings(e.g.chronicatopic
dermatitis)
• fissure:alinearslit-likecleavageoftheskin
• excoriation:ascratchmark
• erosion:adisruptionoftheskininvolvingtheepidermisalone;healswithoutscarring
• ulcer:adisruptionoftheskinthatextendsintothedermisordeeper;mayhealwithscarring
• xerosis:pathologicdrynessofskin(xeroderma),conjunctiva(xerophthalmia),ormucousmembranes
(xerostomia)
• atrophy:histologicaldecreaseinsizeornumberofcellsortissues,resultinginthinningordepressionof
the skin