L3 + 4 Response of Skin to Injury

Question 1

what are the 4 portals of entry for pathogen?

Answer 1

1. epidermal barrier eg/ trauma, excessieve moisture 2. adnexal barrier eg/ penetration through follicular opening 3. vessels eg/ drugs toxins in blood 4. support structure eg/ extension from adjacent lymph node, bone fracture

Question 2

list three acute responses of the epidermis to injury

Answer 2

• vesicles - pustules - necrotising disease also would have accepted: - hyperplastic epithelium - ulcerative - erosion - spongiosic - hydropic degen - erythema

Question 3

a cat presents to you with allergic dermitis. describe the lesion, is it acute or chronic? describe the pathogenesis. what is another other potential cause?

Answer 3

lesion = erythema; redness of skin due to capillary congestion

acute

pathogensis: foregin ag deteced –>macrophage release cytokiens –> inflam, hyperaemia ???

two other potential causes: flea bite hypersensitivity reaction

Question 4

what is a vesicle? where are they located? are they an acute or chronic response? list some causative agents

Answer 4

vesicle = fluid filled blister in superficial epidermis

acute response

nb: only vescile if <1mm, if >1 = bulla
cause: viral infection eg/ vesicular disease (FMD) , thermal burns, drug and allergic reactions, spongiosis (oedema), acantholysis, congentital

Question 5

what three acute lesions can lead bulla/vescile formation? describe them and inlcude examples of causes

Answer 5

1. spongiosis - intracell oedema
2. hydropic degen - intracell oedema + swelling of cells
3. acantholysis - cells split due to disruption of desmosomes, lost adhesiveness

CAUSATION

spongiosis - stapphylococcus sp.

hydropic degen - poxvirus, herpesvirus, superfifical trauma

Question 6

the following histo depictes the three different major vesicle formation pathways. Match A B and C to acantholysis, spongiosis and hydropic degeneration w/ reasoning.

Answer 6

A = spongiosis - intracell oedema w/ seperation of cells yet still in take by desmosomes.

B = hydropic change - swelling of cells

C = ancantholysis - cells split,lost adhesiveness, no desmosomes seen in histo

Question 7

a farmer presents you his pig. what is the lesion, is it acute or chornic, what are some possibel causes?what are the consequesnces of this lesion?

Answer 7

lesions = vesicle

acute

causes: vesicular disease, eg/ FMD, thermal burns, drug and allergic reactions, spongiosis (oedema), acantholysis, congentital
consequences: ulceration, eroision

Question 8

what is this lesion? what are some potential causes? is it chornic or acute?

Answer 8

lesion = pustule; intraepidermal or subepidermal vessicle or bulla filled w/ neutrophils

causes: bacteiral skin disease, phemhigs foliaceus (immune mediate disease, pustures formed because Ab attach desomsomes)

acute

Question 9

what are necrotising diseases of the skin characterised by?

Answer 9

keratinocyte death

Question 10

what are the three broad categorical causes of necrosis? provide examples of each. what are the consequences of necrosis?

Answer 10

phsyical - chemical/thermal burns, radiation

chemical - contact dermititis, toxic epidermal necrosis

vasculitis - ischaemia, infarction

consequences: ulceration and eroision

Question 11

match the picture to the description:

on the left is eroision/ulceration

on the right is eroision/ulceration

Answer 11

left = erosion: loss of epidermis

right = ulceration: loss of epidermis and dermis

Question 12

List some examples of chronic lesions of the skin in response to injry:

Answer 12

• hyperkeratosis
• seborrhoea
• lichenification
• callus
• comedone
• acanthosis

Question 13

what is this representative of?

Answer 13

scale - accumlative losse component of stratum corneum, excess keratin formation

Question 14

describe the pathogenesis of scale/ hyperkeratosis

Answer 14

• any alteration in the following steps of making stratum corenum

(normal steps below)

1. corneocyte have protein core surrounded by ridgid cornified envelope
2. corneocyte layered between hydrolipid formed by lamellar bodies and glandular secretions
3. space b/w cells filled w ceramide, cementing cells
4. acid phosphatase enzyme shed in stratum corenum disolve attachement and permit shedding of superficial dead cells.

Question 15

what is this lesion? is it chronic or acute?

Answer 15

lichenification - chronic

thickened and leathery skin, all layers including s. corneum and epidermis

Question 16

what are some causes of primary hyperkeratosis?

Answer 16

• congential ichnthysosis
• zinc responsive deficiency
• sebaceous adentitis
• vitamin A deficiency
• lymphoma
• sacroptic mange

Question 17

what is acanthosis? is it chronic or acute?

Answer 17

eipdermal thickening of s. spinosum

chronic

ALWAYS PRESENT W/ CHRONIC SKIN Dx OF ALL CAUSES

Question 18

what is this lesion? is it chornic or acute? how are they caused?

Answer 18

lesion: callus, localised hyperplastic lesion

caused by localised pressure or friction

chronic

Question 19

what is this lesion? is it chronic or acute?

Answer 19

comedone

chronic

hair follicle dilated and plugged w/ keratin and lipids

Question 20

List the responses of the dermis to injury

Answer 20

• dermal atrophy
• fibrosis
• dermatitis; inflammation