Derm 3 Flashcards
Function of the skin
Skin layers
-epidermis
-dermis
-subcutis
Layers of epidermis
Dog and cat epidermis
-typically 2-3 cell layers thick
-except thicker for footpads and nasal planum
Main cell types in the epidermis
-keratinocytes
-langerhans cells
-melanocytes
Keratinocytes
-make up 80% of epidermis (keratin intermediate filaments)
-held together by desmosomes and hemidesmosomes therefore keeping skin together
Desmosomes
-anchor keratin filaments
-mediate strong cell-cell adhesion
-allows for tensile strength and mechanical resistance
Keratinization/cornification
Dead keratinocytes = corneocytes
Stratum basale
-mitotically active
-attach to basement membrane and other keratinocytes through desmosomes
Stratum corneum
Stacked layers of anucleate, flat cornified cells (involved corneocytes and lipids)
Function of stratum corneum
-mechanical protection
-barrier to water loss
-barrier to permeation of soluble substances in environment
Epidermis replenishing
Cell production=cell exfoliation
-replenished in stratum basale
-normal migration= 22 days
-normal exfoliation is not visible
Langerhans cells
Antigen processing and presenting cells present in the epidermis
Melanocytes
-present in epidermis
-cosmetic entity, barrier against ionizing radiation, scavenger of cytotoxic radicals and intermediates
-part of developmental and inflammatory processes
Pemphigus foliaceus
-affects epidermis through targeting desmosomes
-autoimmune disease causing pustules and crusting
Ichthyosis
Congenital skin disorder causing issues with differentiation of keratinocytes in epidermis
eg. excessive scaling in golden retrievers
Canine cutaneous histiocytoma
Disease of langerhans cells
-typically benign masses found in young dogs
-usually spontaneously regress
Colour dilution alopecia
-disease of melanocytes causing dilution of hair coat
-hair shafts habe larger than normal pigment granules = loss of hair and recurrent skin infections
Basement membrane zone
-interface between epidermis and dermis
-anchor epidermis and dermis, maintains tissues architecture, wound healing, barrier, nutritional transport
Epidermolysis bullosa
-a group of hereditary disorders
-targets the anchoring complexes of epidermis
-causes ulcers of stressed skin = bony prominences, pressure points
Dermis
-part of connective tissue system
-contains blood, lymph vessels, nerves, epidermal appendages
*modulates wound healing and structure and function of epidermis
Fibres present in the dermis
- collagenous fibers = provides tensile strength
- elastins= elasticity
Mucin
-disease of dermis
-causes wrinkling
-common in Shar pei dogs
Ehlers Danlos syndrome
-inherited disorder affecting connective tissue = fragility and hyperextensibility of skin = tearing
Deep infections in dermis
Body will try and wall it off = nodules in the dermis
*only occurs when something is happening deep within the skin, not disease of dermis
Functions of hair
-physical barrier against trauma
-protection from UV radiation
-thermoregulation/insulin
-repelling water
-source of cells for re-epithelialization during wound healing
Components of hair folicles
-medulla
-cortex = pigment
-cuticle
Sinus hairs
Whiskers
-slow adapting mechanoreceptors
Tylotrich hairs
-scattered amongst normal hair
-rapid acting mechanoreceptors
Stages of hair growth
Sebaceous glands
Distributed through haired skin
-produce sebum, and provides chemical barrier and makes skin and hair softer/moisturized
Alopecia X
-abnormalities in sex hormone receptor function that acts on level of hair follicles
Sebaceous adenitis
-disease of sebaceous glands
-loss of sebum = severe scaling and follicular plugging
Subcutis
Deepest, thickest layer
-provides protection and acts as energy reserve
Where is subcutis absent?
-pinna
-external ear canal
-eyelid
-anus
Post-rabies vaccination panniculitis
-common in poodles, chihuahuas, Bichon Frises, Maltese
-occur at site of vaccination=hair loss, pigmentation, inflammation
External ear canal and pinnae
Collect sound waves and transmits sound waves to tympanic membrane and auditory ossicles
External ear canal structure
-has both vertical and horizontal canals
Cerumen
-normal emulsion that coats the ear canal
-forms protective barrier
Components of cerumen
-desquamated keratinized squamous epithelial cells
-secretions from cerumen and sebaceous glands
-immunoglobulins
Tympanic membrane
Separates external canal from middle canal
-composed of 2 sections:
1. Pars flaccida= upper part; blood vessels
2. Pars tensa = lower part= manubrium of the malleus
Clinical signs of ear disease
-head shaking
-scratching
-otic discharge
-Otitis media/interna= facial nerve paralysis, head tilt, vestibular signs
Anal sacs
Paired invaginations of skin between muscles of internal and external anal sphincters
-connected to surface by single duct
(located at 4 and 8 oclock)
Components of walls of anal sacs
-fibrous connective tissue
-large sebaceous glands
-epitrichial sweat glands
Anal sac impaction
-more common in small breeds; might be linked with obesity and intestinal disorders
-see change in character (secretion, muscle form, fecal form)
Anal pruritus
-can be an anal gland issue, but also commonly allergies!
*dont make assumptions
Anal sac neoplasia
-most commonly adenocarcinoma
-often metastasizes
