Skin structure ,function and infection

Question 1

What are the names of the barriers of the skin

Answer 1

There are 4 barriers of the skin .

> Microbiome barrier
Chemical barrier
Physical barrier
Immune Barrier

Question 2

What is the function of the Microbiome ?

Answer 2

> It forms the normal flora
It inhibits the pathogen colonization / proliferation
Hydrolyzes lipids to form epidermal lipids and maintain pH
Regulates keratinocytes cytokine and AMP secretion
Regulates T cell differentiation

Question 3

What is the function of the chemical barrier

Answer 3

1.Acidic pH
>Sustain normal flora and provides conducive environment for production and function of epidermal lipids and antimicrobial substances

2.Antimicobial peptides
>Defensins and cathelicidins are produced by keratinocytes and other cells .There is a differential production in follicular and intrafollicular skin. The antimicrobial peptides function by disrupting microbial cell wall

Question 4

What is the function of the physical barrier of the skin

Answer 4

1. Stratum basale: Contains mitotically dividing stem cells. Keratins 5 and 14 are major products of basal keratinocytes
2. Stratum spinosum: (lamellar bodies are formed )Keratins 1 and 10 replace 5 and 14 when basal keratinocytes migrate into the stratum spinosum
3. Stratum granulosum:(keratohyalin granules=filagrin precursor ) The major product of keratinocytes in this layer is the filaggrin which induces the aggregation of keratins. The lipids from lamellar bodies
4. Stratum lucidum and corneum : refer to slides

Question 5

Classification of skin infections

Answer 5

1.Superficial
> Impetigo(epidermis ) :Causes loss of the stratum corneum causing lesions and erupt ulcers .Patients do not normally get fever.

> Erysipelas (Epidermis and superficial dermis ): Can extend to deeper dermis .Usually blocks the lymphatic and results in swelling.Patient can get fever . Has boader

2.Deep :
> Cellulitis (extends to subcutaneous layer): Infection spreads to subcutaneous tissue and lacks boarders around infections

> Fascitis ( Extends to superficial and deep fascia ) : Has areas of necrosis because it
disrupts blood vessel plexuses.

> Superficial : Folliculitis (Infection of the hair follicle )

> Deep :
*Furuncle (Extension of folliculitis )

• Carbuncle : Extension into subcutaneous tissue with multiple abscesses

Question 6

Discuss the pathophysiology of burns by discussing the zones

Answer 6

1. Zone of coagulation: Area of insult with immediate cells death and coagulation of of cellular necrosis : irreversible damage
2. Zone of stasis : Damage less severe but microcirculation damaged and therefore stasis occurs .It initially appears viable but may become necrotic after some few days.
3. Zone of hyperemia Area of vasodilation due to inflammation .In burn >20-25% of body area ,inflammation and neural stimulation can cause the zone of hyperemia to extend to the entire body producing a systemic response

Question 7

T/F : Ineffective treatment can extend depth of burn through zone of stais and zone of hyperaemia

Answer 7

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Question 8

Epidermal / First degree burn

Answer 8

> Epidermal injury : S.Basale intact
Erythema ,painful ,dry skin ,no blisters ,capillary refill present
Heal spontaneously without scars ,depending on the extend of the injury

Question 9

Partial thickness (Second degree )

Answer 9

> Superficial /Superficial or mid dermal
Epidermis and papillary dermis and almost reticular dermis
Blisters ,erythma ,painful ,capillary refill present / sluggish
*when blisters are removed ,dermis is pink/white

Question 10

Full thickness (third/ fourth degree)

Answer 10

Extend to subcutaneous tissue/
muscle/ bone
•
White/ black (eschar), waxy appearance
no capillary refill or sensation
•
Do not heal spontaneously, scar

Question 11

Infections in burns

Answer 11

•
Systemic changes
–
Immunosuppression; increased gut permeability
•
Disruption of barrier function at site of injury
–
Depth and extent of burn wound (necrotic tissue)
•
Early debridement of deep partial thickness or full thickness
wounds
–
Change in microbiome at the burn margin and donor
sites Plichta et al. al.,
–
Change in epidermal lipids and antimicrobial peptides
at the burn margin and donor sites Plichta et al. al.,
–
Possible implications for future treatments