Derm and Repro Flashcards
What cells are located in the epidermis
-Keratinocytes- 4 layers of squamous epithelium (Stratum corneum, granulosum, spinosum, and basale)
-Melanocytes
-Langerhans cells (dendritic cells)
What is the most abundant cells in the epidermis
the keratinocytes, organized into distinct vertical zones of stages of differentiation. Important in understanding physiologic and pathological changes
What is the most superficial layer of the epidermis
stratum corneum
what cell type are the keratinocytes of the epidermis
squamous epithelium
What is the most bottom layer of the epidermis?
Stratum basale- 1 layer thick and functions in keratinocyte proliferation and anchoring epidermis to the dermis (hemidesmosomes)
Hemidesmosomes
how the stratum basale layer attaches to the basement membrane
What is the second to last layer of the epidermis
Stratum spinosum- 1-2 layers of haired skin (>20 in non-haired skin) does cell to cell mediated attachment through desmosomes (intracellular) and tonofilaments (intracellular filaments that anchor desmosomes to the cell membrane)
Tonofilaments
intracellular filaments that anchor desmosomes to the cell membrane
Stratum granulosum
the layer under the stratum corneum that is 1-2 layers when present. Squamous cells with distinct basophilic cytoplasmic granules
have lamellar granullars that contrain phospholipids that are extruded into the intercellular space and also keratohyalin granules that contain fibrous proteins (filaggrin) that provide strong cross-linking of cells
Lamellar granules
granules of the stratum granulosum that contain phospholipids that are extruded into the intercellular space
Keratohyalin granules
granules of the stratum granulosum that ocntain fibrous proteins (filaggrin) that provide strong cross-linking of cells
Stratum corneum
the outermost layer of the epidermis. Thin squamous, anuclear cells. not truly dead
form a resistant protective layer/barrier (anchored by intercellular hydrophobic phospholipid “mortar”
Acanthosis
hyperplasia of the stratum spinosum
Hyperkeratosis
hyperplasia of the stratum corneum
Generally, the rate of skin cell production equals the
rate of desquamation
Melanocytes
in the stratum basale and produces melanin pigment that injects into the keratinocytes around it.
melanin pigment is for photoprotection
Langerhans cells
dendritic cells located in the stratum basale and spinosum that function to trap and process antigen (immune surveillance)
Macule
a flat, distinct, discolored area of skin that is less than 1cm
Patch
a macular lesion (flat, distinct, discolored) that is greater than 1cm in diameter
Papule
a solid, elevated, firm, circumscribed lesion that is less than 1cm in diameter. that is caused by the infiltration of inflammatory cells.
associated with hair shaft (folliculitis) or not
What is the most common cause of papular dermatitis
bacterial pyoderma
Plaque
a primary skin lesion where that is an elevated firm lesion with a flat top >1cm in diameter
ex: feline eosinophilic plaque
Pustule
an elevated accumulation of purulent material within epidermis
ex: bacterial pyoderma
Vesicle
a blister- elevated fluid filled cavity within or below epidermis, <1cm in diameter
Bulla
a vesicle that is >1cm in diameter. typically caused by burns, viral infection, and autoimmune disease
Cyst
epithelial lined cavity filled with fluid or semisolid material. Located in the dermis or subcutis
ex: folliclar or apocrine cyst
Wheal
hive, urtica- raised, solid region of edema, often with irregular borders
Ex: insect bite, type 1 hypersensitivity reactive
Nodule
a raised, firm round lesion >1cm in diameter
ex: neoplasia, bacterial or fungal infection, sterile granulomas
Epidermal collarette
a flat to minimally raised scale arranged in circular rim
ex: superficial bacterial pyoderma, fungal infections
Dermis cellular contents
fibroblast, macrophages, T cells, mast cells
Dermis acellular components
for structural support
fibers- collagen, elastin, reticulin
ground substance (fluid) composed of H20, salt, proteoglycans, and glycoproteins
Sebaceous glands
within the dermis, adjacent to follicles with duct that opens into the infundibulum
Basal cells differentiate into sebum producing cells which die, releasing sebum into duct
responsible to hormones (androgens increase activity, estrogens and glucocorticoids lead to atrophy and involution)
Sebum
composed of triglycerides, waxy esters, and contributed to surface oil emulsion on epidermis (moisture and pliancy)
What effect do androgens have on sebaceous glands of the dermis?
increase their activity
What effect do estrogens and glucocorticoids have on sebaceous glands of the dermis?
Atrophy and involution
What is the function of dermis apocrine glands
thermoregulation (sweat) and surface emulsion, antimicrobial components-interferon, transferring, NaCl, complement
Eccrine glands (dermis)
on the paw pads of dog/cat, frog of ungulates, carpus, and snout of pigs
actively secrete product directly onto skin surface
hair follicle stages of growth cycle
1) Anagen phase - growth
2) Catagen phase - transition
3) Telogen phase - resting (end stage)- controlled via hormones, daylight, temperature, nutrition, growth factors
Hypodermis/subcutis/panniculus
the deep layer of fibroadipose tissue
thickness varies based on location, species, and nutritional state
function- insulation, protection, and energy storage
Comedone
a secondary skin lesion where dilated hair follicle is filled with keratin or sebum
ex: chin acne, many endocrine diseases, demodex
Callus
a secondary skin lesion where there is a thick, hard, hairless plaque often located over pressure points (elbow)
Crus (scab)
a secondary skin lesion where dried exudate in the stratum corneum composed of serum, blood, keratin, and degenerate neutrophils
Scale
a secondary skin lesion where loose fragments of keratin on the skin surface (hyperkeratosis) ex: cornification abnormalities, sebaceous adentitis, seborrhea, low humidity
Erosion
a secondary skin lesion where partial loss of epidermis
ex: secondary to ruptured vesicle
Ulceration
a secondary skin lesion where full thickness loss of epidermis with exposure of the dermis
ex: vasculitis
Excoriation
a secondary skin lesion where there is a linear loss of epidermis
ex: scratch or abrasion
fissure
a secondary skin lesion where there is a vertical crack in epidermis to the dermis
Lichenificiation
a secondary skin lesion where there is rough thickened epidermis. Results from chronic scratching/irritation
ex: non-specific chronic dermatitis
How might an infectious agent enter the skin
through epidermal surface, opening of hair follicles or gland ducts, migration along nerves, hematogenous
Pyoderma
pus in the skin where follucular opening is a common portal of entry
superficial and deep bacterial infections
Gross lesions: papules, pustules, epidermal collarettes/epidermitis/folliculitis
Bacterial pyogranulomatous dermatitis
traumatic implantation of saprophytic organisms
Slowly progressive nodular lesion with/without a draining tract.
-Mycobacterial infections
-Botryomycosis (Staph, Strp, Pseudomonas)
-Filamentous bacteria (Nocardia, Actinomyces)
What is a major cause of superficial and deep bacterial pyoderma in the dog
staphylococcus pseudointermedius
What is a major cause of superficial and deep bacterial pyoderma in the horse
staphylococcus aureus of pseudointermedius
What is a major cause of superficial and deep bacterial pyoderma in the pig
staphylococcus hyicus (exidative epidermitis)
What is a major cause of superficial and deep bacterial pyoderma in the sheep, horse, and cattle
Dermatophilis congolensis (Rainrot)
Pyoderma predisposing causes
Allergies, endocrine disease, immune deficiency, matted hair coat, parasitic infection, irritants
Perifolliculitis
inflammation around the hair follicles
Folliculitis
inflammation within the hair follicles
mural - within the follicular wall
luminal- within the follicular lumen
Furunculosis
rupture of the hair follicle resulting in the release of contents into the dermis and secondary foreign body reaction to keratin
other causes: fungus (dermatophytosis) and mites (demodex)
Systemic bacterial infections in skin lesions
bacteremia leading to embolization to skin, bacterial toxins, direct infection of endothelial cells, type III hypersensitivity reaction (immune complexes desposit in vessel walls leading to complement and vasculitis)
Pig differentials for vasculitis
Erysipelothrix rhisiopathiae, salmonella septicemia, procine circovirus 2, others
Vasculitis clinical signs
erythematous plaques or macules dermal edema, hemorrhage bullae, necrosis, well-demarcated ulcerations
Chronicity- regions of alopecia due to atrophy or prior necrosis of hair follicles
Commonly lon paws, pinnae, lips, tails
commonly unrelated to infectious agents- type II drug reaction and type I
Poxvirus infections
caused by many different poxviruses (mostly affect large animals) can cause localized or systemic disease
Epitheliotropic, caused by viral infection of epithelium, vascular injury, induction of epidermal hyperplasia
Microscopic lesions: keratinocyte vacuolization (intracellular edema) -> rupture leading to vesicle, marked epithelial hyperplasia, intracytoplasmic inclusions
how do pox virus cutaneous lesions develop?
Macule -> papule -> vesicle -> umbilicated lesion with raised peripheral rim -> Crust
Contagious pustular dermatitis
ORF- a parapoxvirus of sheep and goats that is zoonotic. lesion distribution typically around lips, muzzle, +/- around the eyes
Dermatophytosis
Common in animals (and humans-zoonotic)
Microsporum canis- lives in dogs and cats, rarely soil
Microsporum gypseum- soil inhabitant- most common in dogs in some regions)
can be localized, multifocal, or generalized
generally confined to the keratin layer if skin and hair
Lesions- patches of alopecia with scaling; papules due to folliculitis/perifolliculities/furuncolosis
Dermatophytosis pathogenesis
Micro-abrasions of stratum corneum help facilitate invasion, produce proteolytic enzymes, penetrate and invade hair shafts, hair damaged, leading to alopecia
Malassezia pachydermatis
a normal inhabitant of the skin and ear canal. Disease seen with correct microclimate (overgrowth) or secondary to other skin conditions like allergies
Erythema, thickening, hyperpigmentation
Diagnosis: cytology, commonly lost during tissue processing for histopatholgy
What are some time mites that cause ectoparasitic infection of the skin?
Demodex and sarcoptes
Demodectic mange
normal commensal inhalant of skin disease- disease associated with overgrowth (stress, corticosteroids, poor nutrition, immuno-incompetence)
Localized or generalized
Localized-one region of body (face most common) with 1-5 areas of alopecia, erythema, scaling
Lesions: folliculitis, perifolliculitis. furinculosis
Diagnosis: deep skin scrapings (mites are in hair follicles), pluck hairs
Sarcoptic mange
burrows into the stratum corneum causing intense pruritus due to hypersensitivity reaction
results in hyperkeratosis and acanthosis due to self trauma
diagnose with superficial skin scraping
What parasite cause eosinophilic/granulomatous reaction
hookworms
Stephanofilaria stilesi
a nematode of the skin, commonly seen in cattle, ventral midline
alopecia and lichanification
Type I hypersensitivity reaction
antigen binds to IgE, complexes bind to mast cells, degranulate, release of histamine and other mediators
can lead to hypersensitivity dermatoses
Type IV hypersensitivity reaction
Cell (T lymphocyte) mediated/delayed hypersensitivity. can lead to hypersensitivity dermatoses
What are some sources of hypersensitivity dermatoses
-insect bites (including flea allergy), atopic environmental allergy, food sensitivity dermatitis
What histological findings do you see with hypersensitivity dermatoses
eosinophilic and mastocytic perivascular dermatitis with dermal edema.
may see some changes associated with self-trauma due to severe pruritus
may see some changes associated with secondary bacterial or malassezia infections
Atopic dermatitis
a common, genetically predisposed allergic skin disease to environmental allergens (hust, mite proteins, plant proteins, mold spores,etc.)
can be seasonal or non-seasonal
Pruritic- skin lesions, generally secondary to self-trauma
erythema, wheal, alopecia, excoriation, salivary staining
chronicity- lichenification and hyperpigmentation
distribution- face,paw, caudal carpi, distal extremities, ear and ventrum
Flea allergy
pruritus of mostly caudal half of animal
Primary skiun lesion- crusted papules, somewhat bulaterally symmetric pattern
Food allergy
non-seasonal pruritis with self trauma
primary lesions (generally not present) erythema, erythematous papules and wheals
Mostly see secondary lesions (same as atopy)
Feline eosinophilic nodular disease
the feline eosinophilic granuloma complex (underlying allergic reaction) that is:
1) Plaque- raised erythematous plaques- ventral abdomen, perineum, and medial thigh
2) Granuloma- papular, nodular or linear lesion skin- skin, mucocutaneous junctions, pawpads, oral cavity
3) indolent ulcer (rodent ulcer)- ulcerated lesion on the upper lip (unilateral of bilateral)
Equine eosinphilic nodular disease
cause is unknown but suspected to be hypersensitiviity. Single or multiple cutaneous papules or nodules (withers, neck, back, other sites) - eosinophilic granulomas
Pemphigus complex
immune mediated, autoimmune disordrs that are associated with pustules and vesicles
antibodies target keratinocytes desmosomes resulting in loss of cell-cell adhesions/ loss of acantholytic cells)
Pemphigus foliaceous
the most common autoimmune condition of horses and cats
2nd most in dogs
Pustules and vesicles that rupture easily
secondary lesions- erosions, crusts, scales
can progress to generalized disease
Pemphigus vulgaris
more severe than Pemphigus foliaceous, rare.
Pustules and vesicles that rupture and result in erosions, crusts, and scales
typically at oral mucosa or combination of oral mucosa, mucocutaneous junctions and skin
occur deep in the epidermis (above the basal cell layer)
Bullous dermatoses
a heterogeneous group of diseases characterized by blistering/ulceration of skin and mucous membrane epithelium following minor mechanical trauma
caused by abnormalities at the level of the dermal and epidermal junction
Bullous pemphigoid
a blistering disease that is caused by abnormalities in the dermal/epidermal junction through disruption in hemidesomoses
Epidermolysis bullosa
a blistering disease that is caused by abnormalities in the dermal/epidermal junction through the basement membrane anchoring fibrils
Cutaneous lupus erythematosus/ discoid lupus erythematosus (DLE) and Systemic Lupus erythematosus (SLE)
a disorder of basal cell injury where antibodies are directed against self-antigens, type III sensitivity with antigen-antibody complex deposition on the basement membrane
this leads to bullae, vesicles, and ulcers
lesions are exacerbated by UV light
Histological lesions is interface dermal/epidermal junction dermatitis with damage to the basal cells. Pigmentary incontinence is secondary to basal cell damage
Discoid Lupus Erythematous (DLE)
a common canine autoimmune skin disease that typically affects younger dogs 2-5 years of age
slow progression
lesions usually restricted to the face, nasal planum depigmentation, erythema, scaling, loss of cobblestone appeaance, dorsal muzzle, lips, perioral, and ears
often confused with mucocutaneous pyoderma
Systemic lupus erythematosus (SLE)
a rare multi-systemic potentially fatal autoimmune disease of dogs and cats resulting in inflammation and tissue damage in the skin, heart, lungs, kidneys, joints, nervous system, or blood
Present as polyarthritis, fever, anemia, thrombocytopenia, glomerulonephritis
Blood test needed for diagnosis- positive for anti-nuclear antibodies (ANA)
Collies, Shetland, and GSD +/- are predisposed to both DLE and SLE
Erythema multiforme/ toxic epidermal necrolysis
a disorder of keratinocyte injury, thought to be host specific T-cell mediated hypersensitivity (type IV) with immune cells directed against keratinocyte-associated antigens leading to single keratinocyte necrosis with surrounding lymphocytes
often induced by drugs: chemicals infectious agents and neoplasia
EM is minor and major based on severity and involvement of mucous membrane
TEN is more severe and life threatening condition that resembles thermal or chemical burns
Uveodermatologic syndrome
an acquired depigmentation disorder common in arctic breeds, thought to be immune mediated rxn to epidermal melanocytes
bilateral panuveitis and bilateral cutaneous depigmentation
Sebaceous adenitis
a disorder of sebaceous glands in dogs (rare in cats) that is suspected to be immune mediated destruction of sebaceous glands leading to alopecia, scaling, and dry/brittle hairs
Histologically see a granulomatous to pyogranulomatous inflammation and epidermal and follicular hyperkeratosis
Chronic disorder leads to a complete lack of sebaceous glands
What are the different mechanisms in which alopecia can occur
1) Follicular dysplasia (abnormal formation)
2) Follicular atrophy (genetic, ischemic, trauma, inflammation
3) Abnormal growth/hair cycle arrest - endocrine, nutritional, metabolic
Color dilution alopecia
See in color dilate animals of many breeds of dogs and cattle. develop alopecia within the first few months to years of life
Black hair follicle dysplasia
alopecia associated follicular dysplasia where bi and tricolor black and white dogs and cattle have alopecia of only black haired region of coat.
Due to clumping of melanin in the pigment in the hair bulb
Congenital Alopecia/Hypotrichosis
Usually a spontaneous genetic mutation resulting in complete or partial hairlessness, hair that is present is typically abnormal
hereditary lack of hair follicles
Alopecia areata
an autoimmune condition targeting hair bulb leading to non-scarring alopecia. characterized by inflammation in or around the follicle bulb
How do you differentiate endocrine alopecia?
there is non-pruritic, bilaterally symmetric alopecia and the remaining hair coat is dull, dry, easily epilated. fails to regrow after clipping
Hair follicles-catagen or telogen phase with lack of hair shafts
What will you see microscopically in animals with endocrine alopecia
the hair follicles are catagen or telogen phase with lack of hair shafts
Hypothyroidism associated alopecia
idiopathic thyroid atrophy or lymphocytic thyroiditis resulting in alopecia because thyroid hormone is necessary for the anagen stage
myxedema is rare