What are the main layers of the skin?
epidermis = keratinocytes and melanocytes
dermis = connective tissue (BV, nerves hair follicles)
subcutis = fat tissue
Give clinical examples of a macule, patch, papule, vesicle, pustule, plaque, ulcer, and nodule.
macule = freckle
patch = measles
papule = eczema
vesicle = herpes
pustule = impetigo
plaque = psoriasis?
ulcer = chancre
nodule = ?
What is icthyosis?
A congenital thickening of the skin, forming numerous large scales (squames)
What is albinism?
Generalized hypopigmentation caused by inborn error of metabolism. Individual lacks enzyme essential for the synthesis of melanin (from aa tyrosine and phenylalanine).
What is epidermolysis bullosa?
Term used for several congenital skin disorders, all characterized by the formation of blisters on rubbing of the skin or minor trauma (usually on palms and soles)
Explain the effects of mechanical trauma on the skin and subQ tissues.
Blunt trauma: usually causes contusion, bleeding into skin and soft tissues.
Laceration: disruption of skin and underlying soft tissue.
What are the differences between first-degree, second-degree, and third degree burns?
1st: erythema and swelling, spotty, single cell necrosis and edema.
2nd: epidermal blisters (spares follicles)
3rd: massive necrosis of entire epidermis and dermis
Compare immersion foot and frostbite.
Immersion foot = exposure to nonfreezing cold and moist environment. small blood vesses, stunned by cold become permanently dilated and unable to regulate local blood flow. venous stagnation >> necrosis >> blisters and ulcers
frostbite = exposure to subfreezing temperature. blotchy, red and swollen with reheating >> gangrene
Describe an "electric mark" on the skin.
Passage of electricity generates hear, which burns the tissues >> linear marks
Compare the effects of acute and chronic sun exposure.
acute = hyperemia, 1st or 2nd degree thermal injury
chronic = skin becomes more birttle, less elastic, develops wrinkles, resist injury less efficiently, skin cancer
Describe and explain the pathogenesis of impetigo, folliculitis, furuncle, and carbuncle.
Impetigo: highly contagious, heals without scars, strep or staph aureusI, honey colored scab, superficial
Folliculitis: limited to hair follicles
Furuncle: bacteria invades hair shaft and extends into perifollicular tissue
Carbuncle: enlarges to include several hair follicles
Compare superficial dermatophytosis with deep fungal infections.
Superficial dermatophytosis >> live in surface area, causing no inflammation of underlying skin
Deep fungal infections >> cause large destructive lesions and tumor like lesions
List viruses that infect skin.
measles, chickenpos, herpes zoster, herpes labialis, HPV
Describe insect bites.
itchy, maculopapular skin lesion with a red dot in the center.
What is scabies?
Caused by a mite. Creates burrows in the superfiical layers of the epidermis. Maculopapular eruptions evolve in reponse ot the bite, feces, or ova
Describe the pathology of acne and explain its pathogenesis.
May have hereditary, hormonal, and bacterial factors.
Hormones: promote hyperkeratosis, blocking discharge of sebum, also sitmulate sebaceous glands
Retained sebum is colonized by bacteria.
What is eczema?
Chronic dermatitis, edema, hyperkeratosis
exogenous = environmental irritants, contact dermatitis
endogenous = autoimmune disorders
What is seborrheic dermatitis?
Chronic disease with reddening, scaling, itching
Especially nasolabial folds, eyebrows, upper chest
Describe the pathologic and clinical features of psoriasis.
Generalized papulosquamous disease
presents with slighly elevated papules and patches >> silvery scales
often on extensor surface of extremities, scalp and nails
Classify skin neoplasms.
- epithelial cells
- pigmentary cells
- dermal connective tissue
- bloodborne immigrant cells
What is seborrheic keratosis?
most common benign epidermal tumor
brownish, solitary/multiple, mulberry shaped, wartlike, exophytic, flat-topped lesion with corrugated furrowed surface
papillae lined with basaloid cells
Compare basal cell and squamous cell carcinoma.
Basal cell: most common malignant epithelial tumor, sun-exposed skin, islands and strands of invasive neoplastic cells resembling those in the basal layer
slightly elevated nodule with a central depression
Squamous cell: malignant, sun-exposed skin, typically locally invasive
plaque, small persistent ulcer
What is actinic keratosis?
1/2 squamous cell carcinoma
similar to cancer, but no invasion of underlying tissue typically >> carcinoma in situ
What are the most important telltale signs of skin cancer?
- persistent, nonhealing ulcer, containing friable, bleeding tissue
- ulcer or nodule of irregular shape and indistince margins
- ulcer surrounded by atrophic and keratotic skin typical of sunlight injury
Compare freckle with lentigo and nevus.
freckle = patch of hyper-reactive melanocytes
lentigo = sharply demarcted macule with increased melanocytes
nevus = accumulation of melanocytes
Classify malignant melanomas.
lentigo maligna flat, macular lesion, originates in a preexisting freckle
superficial spreading of melanoma 70%, irregularly pigmented macules with irregular edges, pruritic, legs (w) back (m)
nodular melanoma vertical growth, infiltrating variant
acral-lentiginous melanoma palms, plantar surfaces, asians/blacks
List the ABCD of diagnosis of malignant melanoma.
A = assymmetry of lesion
B = irregular borders
C = marked variation of color
D = > 6mm usually
What is Kaposi's sarcoma, and how is it related to the AIDS epidemic?
Composed of BV and perivascular connective tissue
AIDs facilitates the prolferation of blood vessls, herpes virus 8?
Compare mycosis fungoides and urticaria pigmentosa.
MF: T cell lymphoma
skin macules/papules > nodules > ulcerating masses
UP: dermal infiltrates of mast cells
brownish-red macules, elevated papules > flare with trouching or stroking
Describe the main features of nail infections.
koilonychia = spoon-shaped nails
clubbing = chronic pulmonary disease
paronychia = bacterial infection of cuticle
onchomycoses = fungal infection