L31 - Basic physiology of skin and Mechanisms of skin diseases Flashcards
List the 5 functions of the skin?
- Thermo-regulation
- Repair of injury
- Immunological defense
- Endocrine function
- Psychosocial function
List the functions of the skin as a physical barrier?
- Prevent loss of water, electrolytes
- Minimize harm by toxic materials
- Prevent infiltration by microorganisms
- Prevent entrance of allergens
- Protect against UV
Describe the effects of Toxic epidermal necrolysis (TEN)?
full-thickness epidermal cell death
Septic shock most likely caused by drug reaction
List conditions/ diseases that arise from defective skin barrier against dehydration and electrolyte loss?
pre-renal failure, hypotension, hypernatraemia
List 3 types of erythroderma?
psoriasis, eczema, drug eruption
Which layer of the skin acts as a barrier to toxic materials?
Stratum corneum (SC): Dead keratin envelope
Name some conditions that cause defective stratum corneum in skin. Consequences?
Disorders of keratinization
e.g. Darier’s disease, epidermolytic hyperkeratosis
– Less resistant to chemical penetration
– Recurrent bacterial infections
Describe the pathogenesis of Atopic dermatitis?
Loss of function filaggrin gene mutation**
> > lack of ceramides (sphingolipids)
> > more transepidermal water loss
> > epi-cutaneous sensitization by allergens)
Which components of the skin protect against UV light?
– Stratum corneum (reflect, scatter photons)
– Melanin (absorb photons)
Mechanisms of skin thermo-regulation in response to heat?
evaporative cooling, vasodilatation, direct radiation
What type of gland is Eccrine gland? Function and discribution?
Sweat glands for evapourative cooling: secrete hypotonic sweat
Generalized distribution, densely populated in palms, soles, axillae
Mechanisms of skin thermo-regulation in response to coldness?
Muscle exercise (voluntary)
Shivering (involuntary)
Vasoconstriction
Compare the repair capacity of the epidermis and dermis of skin?
– Epidermal = complete regeneration
– Dermis = granulation (scarring)
Define the 3 pathways for complement activation?
- Classical pathway (antigen-antibody complex)
- Alternative (polysaccharides, bacterial cell wall)
- Lectin pathway (microbial carbohydrates)
Name one complement that opsonizes microbes? Name 3 for increasing vascular permeability?
C3b (opsonin)
C3a, C4a, C5a (anaphylatoxins)
Which complements for the membrane attack complex?
Assembly of C5b, C6, C7, C8, C9 = membrane attack complex (MAC)
makes pores in cell membrane = osmotic lysis
Give 2 examples of anti-microbial peptides of skin? Which layer secretes?
– Human β-definsin (HBD) –HBD 1,2,3,4
– Dermocidine
Secreted from epidermis
Which condition is caused by increased expression of HBD-2?
Human β-definsin -2
> > Psoriasis (less bacterial infection observed in these patients)
Function of the skin in the Vitamin D metabolism pathway?
Converts 7-dehydrocholesterol to cholecalciferol (vitamin D precursor)
Describe the effects of glucocorticoids on the skin?
Glucocorticoids: Loosen intercellular connections and reduce epidermis effectiveness
Describe the effects of sex hormones on the skin?
Sex hormones:
- increases epidermal thickness
- accelerate wound healing
- increase dendritic cells protecting against cancer cells
List 4 skin diseases that affects the appearance of skin and psychosocial function?
- Alopecia = hair loss
- Vitiligo (white patches of skin)
- Albinism
- Psoriasis (scaly plaques)
Clinical presentation of atopic dermatitis? Acute, subacute and chronic lesions?
- Ill-defined erythematous scaling patches**
- Highly sensitive to allergens (increased serum total IgE)
Acute lesions: swelling, vesicles
Subacute lesions: discoid-shaped, weeping
Chronic lesions: lichenification
List 4 causes/triggers of Psoriasis?
- Genetic: familial component
- Inflammation: cytokines (IL-1, IL-6…)
- Drugs: Alcohol, hydroxychloroquine, terbinafine, lithium, β blockers
- Infections: Strep., HIV
