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MP321 > topical infections skin > Flashcards

topical infections skin Flashcards

1
Q

functions of skin

A
  • physical barrier to noxious agents and entry of pathogens
  • immunological barrier to the entry of pathogenic organisms
  • assists retention of heat and regulation of temperature
  • retains moisture and maintains osmotic balance within body
  • sensory organ
  • excretion of sweat/salt balance, pheromones, antibacterial peptides
  • vitamin D production
  • protection from UV by melanocytes producing a pigment
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2
Q

skin structure

A
  • waterproof cornified outer layer of keratin proteins and lipids, made by epidermis
  • hair follicle with sebaceous gland and muscle in dermis
  • heat insulating fatty layer of hypodermis
  • apocrine sweat glands: bud fatty secretions off into enclosed areas like hair follicles
  • eccrine sweat glands: secrete directly onto skin surface (thermoregulation, salt excretion, antibacterials)
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3
Q

layers of the epidermis

A
  • germinal layer: stem cells replicate + renew migrating upwards / melanocytes produce pigment
  • spindle layer: cells glued onto a sheet-like structure containing langerhans cells
  • granular layer: vesicles containing keratin fibre which strengthens layer
  • anuclear squamous layer: tough because of tightly joined keratin, dead skin cells constantly shed off
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4
Q

the pilosebaceous unit

A
  • hair follicle bases is in the dermis layer
  • the arrector muscle: when it contracts it pulls the base upright making the hair stand up
  • sebum is produced (sticky substance) it is antibacterial with low pH containing proteins/waterproofing lipids
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5
Q

sensory nerves in the skin

A
  • the meissner corpuscle: responds to light pressure
  • pacinian corpuscles: deeper pressure
  • merkel cells: respond to sustained light pressure
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6
Q

4 stages of wound healing

A
  • haemostasis
  • inflammation
  • proliferation
  • remodelling
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7
Q

haemostasis

A
  • fibrin is released by platelets
  • cross linked to make a plug to stop bleeding
  • preventing infections
  • langerhan cells patrol local area
  • neutrophils recruited
  • release of histamine causes vasoconstriction
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8
Q

inflammation

A
  • chemotactic factors released into bloodstream
  • monocytes move by diapedesis
  • more neutrophils attracted
  • mast cell activation
  • cycle of inflammation
  • combats opportunistic infections
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9
Q

proliferation

A
  • forms scab on top of wound
  • scab detaches as skin regrows
  • endothelial cell proliferation promotes angiogenesis (development of new blood vessels)
  • fibroblast proliferation fills underlying connective tissue and skin
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10
Q

remodelling

A
  • wound edges corm contiguous barrier
  • healing continues underneath
  • myofibroblasts make pseudopods and migrate forward dragging cells behind them
  • enabling ends to come together
  • takes months to fully heal
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11
Q

factors directly affecting wound healing

A
  • body site
  • infection
  • vascular supply
  • oxygenation
  • mechanical stress
  • desiccation (removal of moisture)
  • oedema (build up of fluid causing swelling)
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12
Q

factors indirectly affecting wound healing

A
  • age
  • hygiene
  • diabetes
  • autoimmune diseases
  • venous stasis (inflammation lower legs)
  • predisposition to keloids
  • genetic skin diseases
  • immunocompromised state (AIDS/cancer)
  • obesity/immobility/neuropathy
  • alcoholism/drugs abuse
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13
Q

tanning

A
  • UV light exposure induces double-stranded breaks in DNA in keratinocytes
  • activating p53 protein
  • transcription of proopiomelanocortin (POMC)
  • POMC cleaved into Beta-endorphin (local analgesic) and Alpha-melanocyte stimulating hormone (MSH)
  • MSH causes melanocytes to produce pigment which is transferred to keratinocytes by melanosomes
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14
Q

melanomas

A
  • arise from transformed melanocytes
  • hardest to treat
  • invasive and needs early detection
  • triggered by UV
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15
Q

non-melanoma skin cancer

A
  • very common
  • removed by freezing off
  • not as dangerous as melanoma
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16
Q

squamous cell carcinoma

A
  • top layer of epidermis
  • forms as a lesion on top of skin
  • common on nose/forehead/top of head
17
Q

basal cell carcinoma

A
  • germinal layer of skin then invades tissue
18
Q

vesicles

A

fluid filled blisters the size of a pin head

19
Q

bullae

A

fluid filled blister-like eruptions around 1cm in diameter

20
Q

acne vulgaris

A

causes: blockage of the pilosebaceous unit can allow infection (propionium bacterium acnes) and formation of pustules
symptoms: if infection severe and hair follicle ruptures can cause scarring
treatment: topical benzoyl peroxide, tetracycline considered if symptoms severe

21
Q

impetigo

A

causes: s. aureus, s. pyogenes
symptoms:
- non-bullous type has pinhead pustules on red skin which erupt to give yellow-brown crust (after injury)
- bullous type has larger blisters which release clear yellow liquid to leave golden yellow crust (s. aureus)
treatment: topical treatment with bacitracin or mupirocin

22
Q

ecthyma

A

causes: progresses from untreated impetigo
symptoms: infection penetrates to deeper layers of skin causing appearance of painful ulcers
treatment: warm compresses and antibiotics (dicloxacillin)

23
Q

folliculitis

A

causes: infection of hair follicles by s. aureus, affects beard/armpit/back of neck
signs and symptoms: red pustules form and rupture in a few days
treatment: self-limiting and resolve naturally, topical clindamycin and erythromycin if necessary and anti-bacterial soap, larger abscesses may be surgically removed

24
Q

erysipelas and cellulitis

A

causes: involves lymphatic vessels, erysipelas caused by s. pyogenes and cellulitis by s. aureus
symptoms: painful, warm, red swelling forming well defined plaque
treatment: erysipelas: penicillin, cellulitis: dicloxacillin

25
Q

necrotising fasciitis

A

causes: infection of subcutaneous tissue can occur after surgery/trauma, can be caused by s. pyogenes or mixture of bacteria
symptoms: warm red skin but lesion rapidly expands and tissue becomes dark, pustular then necrotic with gangrene
treatment: surgical intervention with parenteral antibiotics

26
Q

mycobacteria

A

lupus vulgaris: brown nodules on face
leprosy: brown nodules, white patches on skin and neuropathy

27
Q

fungal infections of the skin

A
  • dermatophytosis
  • trichophyton rubrum is most common infectious fungus
  • fungal infections involve: trichophyton, microsporum, epidermophyton
28
Q

forms of tinea

A
  • tinea pedis (athletes foot)
  • tinea cruris (jock itch)
  • tinea capitis (cradle cap in babies)
  • tinea corporis (ringworm)
  • tinea unguium (onychomycosis) infection of nails
    topical treatment: terbinafine/clotrimazole/econazole
29
Q

tinea versicolor

A

causes: widespread yeast malasseiza furfur more common in hot climates
symptoms: lightened pigmentation of the skin in upper body/limbs
treatment: selenium sulphide shampoo or topical antifungal agents

30
Q

candidiasis

A

causes: yeast candida albicans (normal microbiota), poor oral hygiene and dentures
symptoms: inflamed and itchy membranes in moist mucous tissues such as mouth/vagina/armpits
treatment: topical antifungals, systemic antifungals such as ketoconazole/fluconazole

31
Q

herpes simplex (type 1) and cold sores

A

causes: antibodies to HSV type 1, virus resides in dorsal ganglia until reactivated
symptoms: self limiting eruption around mucous membranes of mouth
treatment: aciclovir favoured treatment

32
Q

herpes varicella zoster (chicken pox/shingles)

A

causes: virus travels to sensory ganglia where it remains for life
symptoms: pain, paraesthesia (burning sensation) in an affected dermatome
treatment: resolves with rest and analgesics, aciclovir can be used

33
Q

warts

A
  • benign skin tumours caused by HPV
  • have dark necrotised blood vessels at heart of wart
  • common wart affects hands/face/knees and can spread
  • plantar wart grows into skin of foot causing pain
  • can resolve but can be removed by chemical cryo/surgical ablation
  • genital warts can increase risk of cervical cancer
34
Q

molluscum contaginosum

A

causes: pox virus, transmitted by direct skin contact
symptoms: hyperplasia raised pink, pus filled lesions with central depression
treatment: can linger in immunocompromised individuals similar treatment options for warts with addition of curettage and cantharidin

MP321 (11 decks)

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