Structure, function, diagnostics and therapy Flashcards
Which cells in the skin originate from the neural crest?
Melanocytes
Which are the first hairs to appear on a foetus?
Vibrissae and tactile or sinus hairs
Gene W causes which coat phenotype?
White (pink skin, blue or brown eyes and white hair) - also called albino
All non-white horses are ww
Gene G causes which coat phenotype?
Exclusion of pigment from hair - greying. GG or Gg horses always have pigment in their skin and eyes.
All non-greys are gg.
Gene B causes which coat phenotype?
Black hairs on the points and /or most of the body, the b allele allows black hair in the skin but not the hair (e.g. chestnuts).
Gene A causes which coat phenotype?
The distribution of black hairs e.g. A and B is the bay colour.
Gene C causes which coat phenotype?
Pigment dilution. Fully pigmented horses are CC, heterozygotes are e.g. palomino and cc are cream with pink skin and blue eyes.
Gene D causes which coat phenotype?
Dun patterning
Gene To causes which coat phenotype?
Tobiano spotting
In general, how many cell layers thick is the epidermis in horses?
5 to 7 cell layers
Which body sites show rete ridges in haired skin?
Mane and tail bases
The below proteins make up which epidermal structure? BPAG1/BP 230 Plectin alpha-6-beta-4 intergrin BPAG2/BPAG180/collagen XVII Laminin 5
Hemidesmosomes
Which special stains can be used to identify melanocytes on histopathology?
DOPA reaction
Fontana ammoniacal silver nitrate
Which type of melanin contains a high proportion of sulphur?
Phaemelanins
Dopaquinone is the key intermediate in the metabolic pathway for which substance?
Melanin
Which copper-containing enzyme is the rate limiting enzyme for melanogenesis?
Tyrosinase
Melanosomes originate from which organelle?
Golgi apparatus
Which epidermal cells have high-affinity receptors for Fc-IgG and complement 3, contain membrane associated vimentin, adenosine triphosphatase, CD45, S-100 protein and CD1 and are aurophilic?
Langerhans cells
What is the epidermal turnover time in horses?
~17 days
What effect does inflammation have on skin pH?
Switch from acidic or neutral to alkaline
How thick is the BMZ in haired skin in horses?
1.5-5um
8-15um
25-35um
1.5-5um
Collagen accounts for what % of dermal fibres?
90%
Match the fibres and the stains used to differentiate them:
Collagen
Reticulin
Elastin
Verhoeff and van Gieson stains
Special silver stains
Masson trichrome
Collagen - Masson Trichrome
Reticulin - Special silver stains
Elastin - Verhoeff and van Gieson
The unusual cross-linking of desmosine and isodesmosine gives which dermal fibre it’s remarkable strength?
Elastin
Match the collagen types and their location:
Type IV
Type V
Type VII
Anchoring fibrils
Lamina lucida
Lamina densa
Type IV - Lamina densa
Type V - Lamina lucida
Type VII - Anchoring fibrils
Which stain highlights mast cell granules on histopathology?
Toludine blue
AOG (Acid‐Orcein Giemsa)
True or False:
In horses, a single hair arises from each follicle and is accompanied by sebaceous and epitrichial sweat glands and an arrector pili muscle.
True
The inner root sheath keratinises and disintegrates when it reaches which level of the hair follicle?
The isthmus
Where is the outer root sheath thickest, towards the epidermis or the hair bulb?
Towards the epidermis
Arector pili muscles play a role in thermoregulation and emptying of which glands?
Sebaceous glands
Which proteins are up-regulated on endothelial cells during inflammation?
ICAM-1 (intercellular adhesion molecule)
VCAM-1 (vascular cell adhesion molecule)
Name three breeds of horse predisposed to atopic dermatitis
Quarter Horse Thoroughbred Warmblood Arabian Morgan
Name three breeds of horse predisposed to insect bite hypersensitivity
Icelandic Friesian Quarter Horse Warmblood Shire Shetland Connemara
Which two species of Demodex mites can be found on horses?
Demodex equi
Demodex caballi
Which topical antiseptic can destroy fluorescence in cases of dermatophytosis?
Iodine
Which dermatophyte, commonly isolated from horses, does not grow on DTM?
Trichophyton verrucosum
Reticular degeneration is most commonly seen with which acute/subacute inflammatory dermatoses?
Dermatophilosis
Acute contact dermatitis
Hydropic degeneration of basal epidermal cells is usually associated with which diseases?
Cutaneous adverse drug reactions
Lupus erythematosus
Erythema multiforme
Vasculopathies
Cholesterol clefts on histopathology (clear spaces in needle or spicule shape) are seen with which diseases?
Xanthomatosis
Panniculitis
Ruptured follicular cysts
Define desmoplasia
Fibroplasia induced by a neoplastic process
Villi (dermal papillae projecting into a vesicle or bulla) are seen with which diseases?
Photosensitisation
Bullous pemphigoid
Epidermolysis bullosa
Cutaneous adverse drug reactions
Name two diseases that can show diffuse mucinosis
Hypothyroidism
Lupus erythematosus
Which special stain aids visualisation of the BMZ?
PAS
Multinucleated epidermal giant cells are typically associated with which types of infection? Bacterial Protozoal Fungal Viral
Viral infectionss
Which histopathological reaction pattern is typically caused by: Hypersensitivity Ectoparasites Dermatophytosis Dermatophilosis Seborrheic disorders Contact dermatitis
Superficial and deep perivascular dermatitis
Name two diseases that cause diffuse parakeratotic hyperkeratosis with perivascular dermatitis
Ectoparasites Dermatophilosis Dermatophytosis Malassezia dermatitis Zinc-responsive dermatitis Hepatocutaneous syndrome
Chymase, tryptase and dipeptidly peptidase II are enzyme histochemical markers of which inflammatory cell?
Mast cell
True or false?
The skin’s permeability to drugs increases as the hydration of the stratum corneum increases
True
True or false?
Astringents precipitate proteins and generally do not penetrate deeply
True
Name two types of occlusive emollients?
Vegetable oils
Animal oils (eg. lanolin, lard)
Hydrocarbons (e.g. paraffin, petrolatum)
Waxes
How do hygroscopic agents work?
They are moisturisers that are incorporated into the stratum corneum and attract water.
Give two examples of a hygroscopic agent
Propylene glycol Glycerin Colloidal oatmeal Urea Sodium lactate Carboxylic acid Lactic acid
What dilution of chlorhexidine is non-irritant and suitable for wound irrigation?
0.05%
Below which concentration is urea a humectant and not keratolytic?
20%
What are the well known adverse effects of DMSO?
Garlic-like odour
Increased warmth and/or pruritus (histamine release, exothermic with water)
Dehydration (too hygroscopic)
Zinc oxide and titanium dioxide are examples of which type of sunscreen,
physical or chemical?
Physical; they form an opaque barrier
Horses show highest blood cortisol concentrations at which time of day?
In the morning - oral steroids should be given at this time
