Flashcards in CH19 - Skin Pathology Deck (143)
What is the function of skin?
It is a barrier against environmental insults and fluid loss
What is skin composed of?
an epidermis and dermis
What is the epidermis comprised of?
keratinocytes and has four layers
What are the layers of the epidermis?
1) Stratum basalis 2) Stratum spinosum 3) Stratum granulosum 4) Stratum corneum
What is the stratum basalis?
regenerative (stem cell) layer
What is the stratum spinosum?
Its characterized by desmosomes between keratinocytes
What is the stratum granulosum?
It is characterized by granules in keratinocytes
What is the stratum corneum?
It is characterized by keratin in anucleate cells
What does the dermis consist of?
connective tissue, nerve endings, blood and lymphatic vessels, and adnexal structures (e.g., hair shafts, sweat glands, and sebaceous glands)
What are the inflammatory dermatoses?
1) atopic (eczematous) dermatitis 2) contact dermatitis 3) acne vulgaris 4) psoriasis 5) Lichen Planus
What is atopic (eczematous) dermatitis?
Pruritic, erythematous, oozing rash with vesicles and edema; often involves the face and flexor surfaces
What are flexor surfaces?
Elbow, wrists and knees
What is type 1 hypersensitivity reaction associated with?
asthma and allergic rhinitis
What is contact dermatitis?
Pruritic, erythematous, oozing rash with vesicles and edema
When does contact dermatitis arise?
upon exposure to allergens
What are the allergens for contact dermatitis?
1) Poison ivy and nickel jewelry (type IV hypersensitivity) 2) Irritant chemicals (e.g., detergents) 3) Drugs (e.g., penicillin)
What is the treatment for contact dermatitis?
It involves removal of the offending agent and topical glucocorticoids, if needed.
What is acne vulgaris?
Comedones (whiteheads and blackheads), pustules (pimples), and nodules; extremely common, especially in adolescents
What is acne vulgaris due to?
chronic inflammation of hair follicles and associated sebaceous glands
In acne vulgaris, how are comedones formed?
There is hormone-associated increase in sebum production (sebaceous glands have androgen receptors) and excess keratin production block follicles
What are propionibacterium acnes?
It is infection that produces lipases that break down sebum, releasing proinflammatory fatty acids; results in pustule or nodule formation
What is the treatment for acne vulgaris?
Treatment includes benzoyl peroxide (antimicrobial) and vitamin A derivatives (e.g., isotretinoin), which reduce keratin production.
What is psoriasis?
Well-circumscribed, salmon-colored plaques with silvery scale, usually on extensor surfaces and the scalp; pitting of nails may also be present.
What is psoriasis due to?
excessive keratinocyte proliferation
What is the etiology for psoriasis?
Possible autoimmune etiology
What is psoriasis associated with?
For psoriasis, what happens if there is an environmental trigger?
lesions often arise in areas of trauma (environmental trigger)
What does the histology for psoriasis show?
1) Acanthosis (epidermal hyperplasia) 2) Parakeratosis 3) Collections of neutrophils in the stratum corneum (Munro microabscesses) 4) Thinning of the epidermis above elongated dermal papillae; results in bleeding when scale is picked off (Auspitz sign)
What is parakeratosis?
hyperkeratosis with retention of keratinocyte nuclei in the stratum comeum