Dermatology: Structure & Function Flashcards
Dermatophagoides farinae
Feed on dead skin cells – “house mites”
Bacterial Dysbiosis
when there is a shift in skin microbiome, favoring opportunistic bacteria leading to atopic dermatitis (allergic rxns)
Epidermis
What are the 4 layers of the epidermis layer of the skin? What is the importance of knowing these different layers?
Different conditions affect different layers of the epidermis (e.g., Pemphigus foliaceus => SG & SS)
Epidermis
Function of Stratum Basal
skin cell regeneration
Epidermis
Function of stratum spinosum
thickest layer (squamous cell layer – keratinocytes and Langerhans cells)
- thicker at the footpads, nose and mucocutaneous junction
Epidermis
Components / function of Stratum granulosum
Dense packing of basophilic keratohyalin granules (lipids + desmosomal interactions) – help to form a waterproof barrier that functions to prevent fluid loss from the body.
Epidemis
Composition and function of Stratum corneum
- Terminally differentiated (dead, low-nutrient, anucleated) keratinocytes that are constantly being shed
- Layers of corneocytes - function as a physical, chemical and immunological barrier
Epidermis
Function of the corneocyte layers in Stratum Corneum
the corneocyte layers are like bricks, mortared together by lipids/desmosomes, creating the water impermeability of the epidermis
Epidermis
Define cornification and epidermal cell renewal time
The process in which the stratum basale cells differentiates into stratum corneum via an active process (requires ATP!!)
Epidermal cell renewal time = time it takes for SB cells to differntiate into SC cells
Turnover requires a delicate balance of replacement & replenishment
- if too many daughter cells being replenished, but not enough being shed, -> thicker skin
- if too much shedding but not enough replenishment, -> thin, raw skin
Epidermis
Desmosomes - functions
Structures that keep the keratinocytes (cells within the epidermis) strong and keep the skin intact
Epidermis
What are the 3 junctions of the epidermis and their functions?
Adherence, tight, and gap junctions
Epidermis
What is the importance of the Basement Membrane Zone?
Region that allows for the basal cells to anchor to the basement membrane and keeps the epidermis intact. If this didn’t occur, the whole epidermis would fall apart!
Dermis
Fibroblasts - function
Produce the ECM (proteoglycans, HA,, etc.) and collagen fibers => structural components of skin!
Dermis
What are the epidermal appendages?
Sebaceous glands, hair follicles
Type of hair follicle?
Simple
Only one hair follicle emerging from one opening
Type of hair follicle?
Compound
>1 hair follicles emerging from one opening
What are the 3 phases of the hair cycle?
- Anagen (growing phase)
- Catagen (transition phase, signals end of active growth phase)
- Telogen (resting phase)
Some breeds have shorter / longer phases than others
Poodles: long anagen phases
Bulldogs: long telogen phases
Identify the regions of the nasal planum
Functions of the Foot Pad
Copious blood & nerve supply++
Functions of the claw
Prehensile (gripping)
Locomotion
Defense and offensive apparatus
Canine Symmetric Lupoid Onychodystrophy (SLO)
- definition
- why is it called “lupoid”
- immune-mediated disease that ONLY affects the claws/nails
- Lupoid = “lupus-like” –> biopsy of the affected nail beds revealed histological features seen in cutaneous lupus erythematosus
Symmetrical lupoid onychodystrophy (SLO) is the most common inflammatory disease to cause abnormal nails in dogs. The etiology of this condition is unknown, but it is suspected to be hereditary or immune-mediated. SLO normally involves multiple nails on all four paws. It’s most commonly seen in middle-aged dogs, around 3 to 8 years of age, but has been seen in both puppies and older dogs. Predisposed breeds include German shepherds, Rottweilers and Gordon setters, but it has been seen in other breeds as well.
The disease often starts as an acute onset of nail loss. Because SLO often starts with a single abnormal nail, it can often take owners a while to realize there is a more generalized nail problem. It may take several months for other nails to be affected or slough off. Nails can also present as dry, distorted claws that do not slough on their own.
One or more of the following abnormalities are typically seen over time:
Onychogryphosis: abnormal curvature of the claws
Onychomadesis: sloughing of claws
Onychorrhexis: fragmentation of the claws
Onychoschizia: splitting of the claws
In some cases (although less commonly), significant inflammation (paronychia) or purulent discharge from the nail bed may be present if there is a secondary bacterial infection. Dogs with this disease may by asymptomatic, but many can have associated discomfort or lameness. SLO is not typically seen with other skin abnormalities or systemic illnesses.
Cutaneous lupus erythematosus (LE) is a diverse group of autoimmune connective tissue disorders localised to the skin that can be associated with systemic lupus erythematosus (SLE) to varying degrees.
Signalement, clinical signs and treatments of Canine Symmetric Lupoid Onchyodystrophy (SLO)
Treatment: doxy + niacinamide (immunomodulatory action); oral-modified cyclosporine (atopica); fatty acid supplmentation; analgesis PRN
How do claws / nails heal in Canine SLO?
Affected dogs heal with abnormal claw formation (onchodystrophy)
