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42 Cards in this Set
- Front
- Back
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What is alopecia?
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absence of hair from areas where it is normally present
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Describe the embryogenesis of the skin
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embryonal stratum germinativum--> hair germs--> buds-->give rise to hair follicles, sebaceous glands, and epitrichial sweat glands. Beneath each bud are mesenchymal cells-->dermal papilla.
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Which of the following is involved with the development of the hair follicle in the embryo?
a. diet b. morphogens c. photoperiod d. temperature |
Morphogens are important for hair follicle development.
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What are the 5 components of hair follicles?
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1.dermal papilla: extension of dermal connective tissue covered by basement membrane
2. hair matrix- nucleated epithelial cells give rise to hair and inner root sheath 3. hair: inner medulla, middle cortex (contains pigment), and outer cuticle 4. Inner root sheath: mold the hair within it 5. outer (external)root sheath: downward extension of the epidermis |
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Where are melanocytes within the hair follicle?
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melanocytes occcur at the matrix
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Describe the glandular structures of the hair adenexae and their function
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Grandular structures act as barriers, used for scent signaling and thermoregulation. Sebaceous glands are present in HAIRED SKIN and are under hormonal control. Sweat glands are neuro controlled.
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The hair growth cycle is made up of 3 parts:
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anagen, catagen, telogen
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Which phase of the hair cycle represents growth?
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anagen
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In which phase does normal hair loss (shedding) occur?
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telogen or resting phase
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What are some intrinsic factors that affect the hair cycle?
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local cytokines, neuropeptides, oncogense
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What are some extrinsic factors that affect the hair cycle?
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extrinsic factors are produced by organs other than the skin. They include genetics, nutritional status, disease stage, hormones (growth hormone, T3, ACTH), immunological, and neural
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What are some external factors that affect the hair cycle?
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photoperiod, ambient temperature, drugs.
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When is the hair cycle most active? least?
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Max activity in summer
min activity in winter |
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What are some intrinsic factors that affect hair structure?
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affected by embryological factors- morphogens/genetics, cell interactions, defective hair pigmentation
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What are some external factors that affect hair structure?
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Anti-mitotic drugs which affect hair cycle
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Alterations in factors that affect hair structure lead to...
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dysplasia
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What is follicular dysplasia?
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abnormally or incompletely formed hair follicle or shaft
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What are some causes of alopecia?
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self trauma (usually assoc. with pruritis)
folliculitis (infection) failure of hair growth cycle dysplastic disorder of hair follicle destruction or absence of hair follicles |
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If alopecia is multifocal what are some ddx?
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infectious, parasitic, or inflammatory
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If alopecia presents symmetically what are some most likely ddx?
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endocrine, hair cycle abnormalities, follicular dysplasia
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If alopecia presents along with systemic disease/signs it is most likely...
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neoplastic or endocrine
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If a young animal presents with alopecia it is most likely:
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developemental/follicular dystrophies/dysplasias or infectious causes
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Diagnostic approach to alopecia includes
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diagnostic tests (skin scrapings, hair pluck/trichography, fungal culture), biopsy, endocrine fxn tests
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why would we perform a skin scraping (what are we looking for)
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parasites
use liquid paraffin or KOH |
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Why would you do a trichography?
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trichography is the miscropic examination of hairs.
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Why would we do a cutaneous cytology? What are we looking for?
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looking for infectious agents...bacterial folliculitis
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Why would we do an acetate tape strip?
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skin- impression smears-surface microbes, cells, surface parasites
hair- surface parasites and eggs, flea dirt |
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When do we perform a Woods lamp exam?
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only for M. canis and M. equinum. Rarely postive in large animals.
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What do we grow fungal cultures in?
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DTM or Sbaourauds
DTM- color change SDA- more colonies |
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When is a skin biopsy appropriate?
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neoplasia, ulcer/vesicle, non-responsive dermatoses, unusual presentations, plan to use harmful txs
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What are some general therapeutic principles to consider when treating alopecia?
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treat the cause, treat incontacts, symptomatic topical therapy, avoid excessive grooming, observe and wait, various systemic therapies to restart hair cycle.
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domestic species have which type of hair follicles?
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compound hair follicles which consist of primary and secondary hairs
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Describe how a hair plucked during anagen phase would look.
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shows a large expanded root that is moist and glistening often pigmented and square at the end
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Describe how how a hair plucked during telogen phase will appear?
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Hair plucked during telogen show a tapered root with little/no pigment
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A hair pluck is performed and most hairs appear to have a tapered root with little to no pigment. What hair growth cycle phase are these hairs under and what might be the problem?
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telogen phase
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Why do animals in poor health exhibit excessive shedding and alopecia?
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in conditions of generalized disease anagen may be shortened resulting in a lot of hair in telogen.
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Which hormones accelerate hair growth rate?
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thyroid hormones and growth hormone initiate and advance anagen
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Which hormones slow hair growth rate?
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excess glucocorticoids and estrogens inhibit anagen and suppress hair growth rate.
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Why do we perform a skin scrape?
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rule out demodex, pruritic ectoparasites
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Why do we perform a hair pluck>
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to assess hair growth phase, presence of fungal infection, shaft defects or pruritis
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When is it appropriate to do a fungal culture?
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pluck hairs and skin scrape for culture. Should be done in ALL CATS and if lesions have an inflammatory component in other species. Dermatophytes!!!
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Why would we perform a cytology
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to assess for bacterial folliculitis, infectious organisms, neoplasia
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