Lab 4: Skin Diagnostic Techniques Flashcards
what tissues make up the ear canal
epithelium
dermis
glands - sebaceous, ceruminous
hair follicles
cartilage
what is the function of the pinnae
- sound localization
- channels sound waves into ear canal
what are the components of the external ear
pinnae
vertical canal
horizontal canal
tympanic membrane
what are the components of the tympanic membrane
pars flaccid (dorsal)
pars tensa (ventral)
what is the significance of a ruptured tympanic membrane visualized on otoscopy
communication between external and middle ear canal
- otitis externa can spread to middle ear
- external ear canal medications can spread to middle ear
what would you expect on cytology of a normal ear
- corneocytes (cornified keratinocytes)
- cerumen
- rare to no yeast
what is earwax and what makes it
cerumen = desquamated keratinized squamous epithelial cells w/ sebaceous + ceruminous gland secretions
function: coat the ear canal
what would you expect on cytology from an ear canal with bacterial infection
presence of rods or cocci bacteria
possible neutrophils + inflammatory cellular debris
what is superficial vs deep skin scraping
superficial: collects broad sample of stratum corneum; does NOT reach dermis
- no bleeding
deep: collects follicular contents; reaches dermis
- bleeds
what kind of parasites can you find on superficial vs deep
superficial: sarcoptes, notoires, psoroptes
deep: demodex
what can a superficial skin scraping without mineral oil be used to evaluate
bacteria and yeast
how can keratinocytes appear on cytology
- flat polyhedral and pale
- folded and darker staining
- linear/cylindrical
parakeratotic: nucleus still present
acantholytic: “blue fried egg”; damage to desmosomes
what infectious agents can be identified on cytology
bacteria - rods and cocci
yeast
occasionally fungal hyphae
what would impression smears be a good diagnostic tool for
- moist, exudative lesions
- pustules
- crusts
- draining lesions
NOT:
- dry/minimally exudative
- small or awkward areas
what would acetate tape be a good diagnostic tool for
- awkward areas (interdigital)
- small areas
- sensitive areas
- dry or greasy skin
NOT:
- wet/exudative skin
- pustules
what would swabs be a good diagnostic tool for
- small areas
- moist, exudative lesions
- ear canals
- contents from pustule
NOT
- dry/minimally exudative
what would scrapings be a good diagnostic tool for
- dry/greasy skin
NOT
- near eyes
- rambunctious patient
- sensitive areas
what is the point of a wood’s lamp
identification of certain dermatophytes that fluoresce “apple green”
what causes fluorescence in dermatophyte infected hairs
pteridine
(tryptophan metabolite)
can a wood’s lamp be used to speciate dermatophytes
NO - speciate by examining morphology of the spores they produce
what type of lesions are best biopsied with punch biopsy
remove skin lesions that are smaller than 8 mm OR to diagnose larger lesions
what type of lesions are best biopsied with a wedge biopsy
deep/wider samples of:
- solitary lesions
- vesicles/bullae
- panniculitis
why are punch biopsies most effective for histopathology
good sample for multifocal or generalized skin lesions
- rapid and repeatable
- does not require anesthesia
- small defect
what circumstances require the use of general anesthesia to obtain a skin biopsy
sensitive areas (nasal planum, foot pads, pinnae
wedge biopsies of deep lesions
what are double punch biopsies used for
sample deeper tissue (deep dermis or panniculus)
what ectoparasites can be diagnosed from a hair pluck
- demodex
- lice (from nits deposited in hair follicles)
- fur mites (cheyletiella)
what do you see in the sample from a color dilute animal
clumping of the melanin within the cortex of the hair shaft
how could evaluating a hair pluck help evaluate alopecia in a cat
if alopecia is caused from self trauma –> hair shafts will be blunt ended or “squared” ends instead of tapered
how can you differentiate a cat hair from a dog hair
cats: serrated/spinous cuticle
dogs: smooth cuticle
