Lab 4: Skin Diagnostic Techniques

Question 1

what tissues make up the ear canal

Answer 1

epithelium
dermis
glands - sebaceous, ceruminous
hair follicles
cartilage

Question 2

what is the function of the pinnae

Answer 2

• sound localization
• channels sound waves into ear canal

Question 3

what are the components of the external ear

Answer 3

pinnae
vertical canal
horizontal canal
tympanic membrane

Question 4

what are the components of the tympanic membrane

Answer 4

pars flaccid (dorsal)
pars tensa (ventral)

Question 5

what is the significance of a ruptured tympanic membrane visualized on otoscopy

Answer 5

communication between external and middle ear canal
- otitis externa can spread to middle ear
- external ear canal medications can spread to middle ear

Question 6

what would you expect on cytology of a normal ear

Answer 6

• corneocytes (cornified keratinocytes)
• cerumen
• rare to no yeast

Question 7

what is earwax and what makes it

Answer 7

cerumen = desquamated keratinized squamous epithelial cells w/ sebaceous + ceruminous gland secretions

function: coat the ear canal

Question 8

what would you expect on cytology from an ear canal with bacterial infection

Answer 8

presence of rods or cocci bacteria

possible neutrophils + inflammatory cellular debris

Question 9

what is superficial vs deep skin scraping

Answer 9

superficial: collects broad sample of stratum corneum; does NOT reach dermis
- no bleeding

deep: collects follicular contents; reaches dermis
- bleeds

Question 10

what kind of parasites can you find on superficial vs deep

Answer 10

superficial: sarcoptes, notoires, psoroptes

deep: demodex

Question 11

what can a superficial skin scraping without mineral oil be used to evaluate

Answer 11

bacteria and yeast

Question 12

how can keratinocytes appear on cytology

Answer 12

• flat polyhedral and pale
• folded and darker staining
• linear/cylindrical

parakeratotic: nucleus still present
acantholytic: “blue fried egg”; damage to desmosomes

Question 13

what infectious agents can be identified on cytology

Answer 13

bacteria - rods and cocci
yeast
occasionally fungal hyphae

Question 14

what would impression smears be a good diagnostic tool for

Answer 14

• moist, exudative lesions
• pustules
• crusts
• draining lesions

NOT:
- dry/minimally exudative
- small or awkward areas

Question 15

what would acetate tape be a good diagnostic tool for

Answer 15

• awkward areas (interdigital)
• small areas
• sensitive areas
• dry or greasy skin

NOT:
- wet/exudative skin
- pustules

Question 16

what would swabs be a good diagnostic tool for

Answer 16

• small areas
• moist, exudative lesions
• ear canals
• contents from pustule

NOT
- dry/minimally exudative

Question 17

what would scrapings be a good diagnostic tool for

Answer 17

• dry/greasy skin

NOT
- near eyes
- rambunctious patient
- sensitive areas

Question 18

what is the point of a wood’s lamp

Answer 18

identification of certain dermatophytes that fluoresce “apple green”

Question 19

what causes fluorescence in dermatophyte infected hairs

Answer 19

pteridine
(tryptophan metabolite)

Question 20

can a wood’s lamp be used to speciate dermatophytes

Answer 20

NO - speciate by examining morphology of the spores they produce

Question 21

what type of lesions are best biopsied with punch biopsy

Answer 21

remove skin lesions that are smaller than 8 mm OR to diagnose larger lesions

Question 22

what type of lesions are best biopsied with a wedge biopsy

Answer 22

deep/wider samples of:
- solitary lesions
- vesicles/bullae
- panniculitis

Question 23

why are punch biopsies most effective for histopathology

Answer 23

good sample for multifocal or generalized skin lesions

• rapid and repeatable
• does not require anesthesia
• small defect

Question 24

what circumstances require the use of general anesthesia to obtain a skin biopsy

Answer 24

sensitive areas (nasal planum, foot pads, pinnae

wedge biopsies of deep lesions

Question 25

what are double punch biopsies used for

Answer 25

sample deeper tissue (deep dermis or panniculus)

Question 26

what ectoparasites can be diagnosed from a hair pluck

Answer 26

• demodex
• lice (from nits deposited in hair follicles)
• fur mites (cheyletiella)

Question 27

what do you see in the sample from a color dilute animal

Answer 27

clumping of the melanin within the cortex of the hair shaft

Question 28

how could evaluating a hair pluck help evaluate alopecia in a cat

Answer 28

if alopecia is caused from self trauma –> hair shafts will be blunt ended or “squared” ends instead of tapered

Question 29

how can you differentiate a cat hair from a dog hair

Answer 29

cats: serrated/spinous cuticle

dogs: smooth cuticle