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MBBS II MSS > L31 - Basic physiology of skin and Mechanisms of skin diseases > Flashcards

L31 - Basic physiology of skin and Mechanisms of skin diseases Flashcards

1
Q

List the 5 functions of the skin?

A
  1. Thermo-regulation
  2. Repair of injury
  3. Immunological defense
  4. Endocrine function
  5. Psychosocial function
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2
Q

List the functions of the skin as a physical barrier?

A
  • Prevent loss of water, electrolytes
  • Minimize harm by toxic materials
  • Prevent infiltration by microorganisms
  • Prevent entrance of allergens
  • Protect against UV
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3
Q

Describe the effects of Toxic epidermal necrolysis (TEN)?

A

full-thickness epidermal cell death

Septic shock most likely caused by drug reaction

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4
Q

List conditions/ diseases that arise from defective skin barrier against dehydration and electrolyte loss?

A

pre-renal failure, hypotension, hypernatraemia

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5
Q

List 3 types of erythroderma?

A

psoriasis, eczema, drug eruption

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6
Q

Which layer of the skin acts as a barrier to toxic materials?

A

Stratum corneum (SC): Dead keratin envelope

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7
Q

Name some conditions that cause defective stratum corneum in skin. Consequences?

A

Disorders of keratinization

e.g. Darier’s disease, epidermolytic hyperkeratosis

– Less resistant to chemical penetration
– Recurrent bacterial infections

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8
Q

Describe the pathogenesis of Atopic dermatitis?

A

Loss of function filaggrin gene mutation**

> > lack of ceramides (sphingolipids)

> > more transepidermal water loss

> > epi-cutaneous sensitization by allergens)

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9
Q

Which components of the skin protect against UV light?

A

– Stratum corneum (reflect, scatter photons)

– Melanin (absorb photons)

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10
Q

Mechanisms of skin thermo-regulation in response to heat?

A

evaporative cooling, vasodilatation, direct radiation

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11
Q

What type of gland is Eccrine gland? Function and discribution?

A

Sweat glands for evapourative cooling: secrete hypotonic sweat

Generalized distribution, densely populated in palms, soles, axillae

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12
Q

Mechanisms of skin thermo-regulation in response to coldness?

A

 Muscle exercise (voluntary)
 Shivering (involuntary)
 Vasoconstriction

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13
Q

Compare the repair capacity of the epidermis and dermis of skin?

A

– Epidermal = complete regeneration

– Dermis = granulation (scarring)

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14
Q

Define the 3 pathways for complement activation?

A
  1. Classical pathway (antigen-antibody complex)
  2. Alternative (polysaccharides, bacterial cell wall)
  3. Lectin pathway (microbial carbohydrates)
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15
Q

Name one complement that opsonizes microbes? Name 3 for increasing vascular permeability?

A

C3b (opsonin)

C3a, C4a, C5a (anaphylatoxins)

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16
Q

Which complements for the membrane attack complex?

A

Assembly of C5b, C6, C7, C8, C9 = membrane attack complex (MAC)

makes pores in cell membrane = osmotic lysis

17
Q

Give 2 examples of anti-microbial peptides of skin? Which layer secretes?

A

– Human β-definsin (HBD) –HBD 1,2,3,4

– Dermocidine

Secreted from epidermis

18
Q

Which condition is caused by increased expression of HBD-2?

A

Human β-definsin -2

> > Psoriasis (less bacterial infection observed in these patients)

19
Q

Function of the skin in the Vitamin D metabolism pathway?

A

Converts 7-dehydrocholesterol to cholecalciferol (vitamin D precursor)

20
Q

Describe the effects of glucocorticoids on the skin?

A

Glucocorticoids: Loosen intercellular connections and reduce epidermis effectiveness

21
Q

Describe the effects of sex hormones on the skin?

A

Sex hormones:

  • increases epidermal thickness
  • accelerate wound healing
  • increase dendritic cells protecting against cancer cells
22
Q

List 4 skin diseases that affects the appearance of skin and psychosocial function?

A
  • Alopecia = hair loss
  • Vitiligo (white patches of skin)
  • Albinism
  • Psoriasis (scaly plaques)
23
Q

Clinical presentation of atopic dermatitis? Acute, subacute and chronic lesions?

A
  • 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

24
Q

List 4 causes/triggers of Psoriasis?

A
  • Genetic: familial component
  • Inflammation: cytokines (IL-1, IL-6…)
  • Drugs: Alcohol, hydroxychloroquine, terbinafine, lithium, β blockers
  • Infections: Strep., HIV
25
Q

Clinical presentation of psoriasis?

A
  • Well-demarcated erythematous scaling plaques on extensor surfaces, scalp
  • Nail changes: Pitting, Onycholysis (separation of nail from nail bed)
  • Association with arthropathy (joint pain)
26
Q

Clinical presentation of contact dermatitis?

A

Usually well-defined border: itchiness, erythema, scaling

Confined to areas with exposure to culprit (e.g. hair dye, ring, cosmetics)

Acute: weeping, vesicles

27
Q

Define the 2 types of contact dermatitis?

A
  1. Irritant contact dermatitis (more common)

2. Allergic contact dermatitis: Type IV HSR

28
Q

Compare between impetigo and erysipelas: Causative pathogen, appearance and affected body part?

A

Impetigo:

  • Staphylococcus aureus
  • Yellow- / honey-colored crusts
  • Peri-oral areas

Erysipelas:

  • Streptococcus pyogenes
  • Well-defined, red, painful patches on face
29
Q

Compare between impetigo and erysipelas: extent of skin involvement and complications?

A

Impetigo:

  • Superficial epidermis
  • Complications: Bullous impetigo, Staphylococcal scalded skin syndrome

Erysipelas:

  • Dermis with lymphatic spread
  • Complications: Lymphedema, Post-streptococcal glomerulonephritis
30
Q

List 2 viruses that causes cutaneous infections?

A

HSV: HSV-1 = herpes labialis, HSV-2 = Genital herpes

VZV: chickenpox, Herpes Zoester

31
Q

List 3 dermatophytes (fungal) that cause cutaneous infection? Which layer of skin is involved?

A

Trichophyton, epidermophyton, microsporum

Superficial fungal infection of skin: stratum corneum / hair / nail (keratin layer)

32
Q

Name 2 skin conditions caused by dermatophyte infection?

A

 Tinea cruris: groin

 Tinea pedis: feet

33
Q

List 2 non-dermatophytes fungi that cause skin infection?

A

Candida, Fusarium

34
Q

Clinical feature of fungal skin infection?

A

Annular scaling patches with advancing border

35
Q

Name one parasitic cutaneous infection?

A

scabies infestation:

hypersensitivity to mites (Sarcoptes scabiei) and their droppings

36
Q

Epidemiology of scabies infestation?

A

elderly patients in elderly homes, hospitals

e.g. by infected bedsheets, clothing

37
Q

Clinical features of scabies infestation?

A

 Severe itchiness

 Discrete papules on limbs / trunk

 Burrows, pustules

MBBS II MSS (31 decks)

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