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List some of the natural skin defences
- Hair - thermal insulation and thermal dissipation
- Melanocytes - photo protection and photosensitisation
- Epidermal barrier - skin surface lipids and stratum corneum
- Innate and adaptive immunity
What are the different layers of the epidermis?
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum corneum
The physical and permeability barrier of the skin is regenerated by the process of ...?
What two factors control desquamation?
- Balance of stratum corneum protease inhibitors and proteases
- Skin pH
List the different portals of entry into the skin via the a) epidermis
b) adnexa c) dermis and panniculus d) underlying tissues
- a) absorption, direct contact, colonisation, penetration, impaired barrier
- b) entry via follicle ostium, rupture of follicle or adnexal glands
- c) blood vessels, nerves (rare)
- d) penetration by damaged bone, extension from adjacent tissues
What are the three different patterns of skin disease?
- Epidemiology - breed, sex, location, season
- Clinical presentation - lesions, distribution, configuration
- Histopathology - pattern analysis
Which breeds are predisposed to skin fold dermatitis?
Sharpei, bulldog, pekinese
What causes symmetrical alopecia in male dogs?
Due to oestrogen production by Sertoli cell tumours in male dogs
What causes cutaneous haemangiosarcoma?
Location - e.g. sun exposure in dogs in Grenada, West Indies
What affect does season have on flea allergy dermatitis?
It is more common in temperate climates and seasonal in colder climates.
What is the difference between primary and secondary skin lesions?
Primary lesions develop spontaneously as a result of underlying skin disease. Whereas secondary lesions evolve from primary lesions or are induce by self trauma or external factors.
Define the following primary skin lesions a) Macule b) Patch c) Papule d) Vesicle e) Bulla f) Pustule g) Wheal h) Cyst i) Nodule j) Plaque k) Tumour l) Abscess
- a) A circumscribed, non-palpable spot characterised by a change in the colour of the skin <1cm
- b) A macule but >1cm
- c) A small solid elevation of the skin <1cm in diameter
- d) Sharply circumscribed epidermal elevation filled with clear fluid. May be intraepidermal or sub epidermal <1cm
- e) A vesicle but >1cm
- f) May be intraepidermal, sub epidermal or follicular. Typically contain neutrophils and bacteria but may contain eosinophils and/or be sterile
- g) A circumscribed raised lesion due to oedema, often transient
- h) An epithelium-lined cavity containing fluid or solid material. Smooth, well circumscribed, usually fluctuant
- i) A circumscribed solid elevation that is >1cm. Usually due to massive cell infiltration that may be inflammatory or neoplastic
- j) A large flat topped elevation formed by extension of coalescence of papules
- k) A mass of 2cm or greater that may be neoplastic or non-neoplastic BUT often the term is used to imply neoplasm
- l) A localised collection of pus in an area of tissue destruction surrounded by inflammation usually more deeply located than a pustule
Describe the following secondary skin lesions a) Collarette b) Excoriation c) Erosion d) Fissure e) Scar f) Lichenification g) Callus
- a) A circular rim of scale that evolves from a pustule, vesicle or bulla
- b) Erosions or ulcers caused by self trauma. Typically linear they indicate pruritus
- c) Loss of part of the epidermis. Depressed, moist, glittering.
- d) Linear crack or break from the epidermis to the dermis
- e) Thickening of the skin with increased creases
- f) Dead keratinocytes plus neutrophils +/- bacteria
List some of the agents of skin disease and give examples of each
- Physical or chemical agents - UV radiation, contact irritants, heat
- Immunological reactions
- Infectious agents - bacteria, viruses, fungi, parasites
- Nurtitional/metabolic disturbance - endocrine disorders, nutritional deficiencies