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what are the 6 main functions of the skin?
- 1. physical barrier prevents: entrance of micro-organisms/chemicals and loss of body fluids/protein
- 2. reduces penetration of UV irradiation
- 3. thermoregulation
- 4. sensory organ
- 5. immune surveillance
- 6. vitamin D production
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what are the 3 main layers of the skin? and what is each made of?
- epidermis: keratinised stratified squamous epithelium
- dermis: collagenous connective tissue
- subcutis: fat, nerve endings, blood vessels
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from the dermis upwards, describe the layers
- dermis
- BM
- (epidermis)
- basal cells
- squamous cells
- keratin layer
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which is the main mechanical layer of the skin?
dermis
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what are the main 5 epidermal appendages?
- hair
- sebaceous glands
- eccrine sweat glands
- apocrine sweat glands
- nails
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what are sebaceous glands?
the appendages of hair follicles
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where are sebaceous glands found?
in dermis throughout body except palms and soles
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what do sebaceous glands secrete?
- sebum
- protective agent to maintain skin texture and hair flexibility
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where are eccrine glands found?
throughout body
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what is primary function of eccrine gland?
- evaporative cooling
- ie sweat glands
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what are apocrine glands? and where found?
they empty into hair follicles in axillary and anogenital regions
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what type of secretion do apocrine glands release?
- odourless secretion
- which is then acted on by commensal bacteria
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when do apocrine glands begin to function?
at puberty
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where in skin does acute eczema affect and why?
epidermis as it is rough and scaly
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where in skin does dermatofibroma affect and why?
its a firm papule and is smooth so its in dermis - pushing up
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where in skin does erythema nodosum occur?
- they are tender, red nodules on shins which occur DEEP
- in fat
- panniculitis
- so superficial biopsy is unhelpful
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what does psoriasis look the same as under microscope?
clear cell acanthoma
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where does lichen planus affect?
- wrists, ankle, genitalia
- mouth: striae
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if there is a melanocytic lesion, what needs to be done?
complete excision
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how can you tell between a melanoma and a mole?
- melanoma: asymmetrical, inflammation, irregular border, variable pigmentation
- mole: symmetrical, sharp lateral cut off
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what is actinic keratosis?
areas of sun damage
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how should actinic keratosis be biopsied?
punch biopsy - as need to get to basal layer where changes occur
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what is a cutaneous horn?
when there is no substance to the base of the lesion
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what is the differential for cutaneous horns?
- actinic keratosis
- viral warts
- SCC
- trichilemmoma
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what are the 3 main types of BCC?
- superficial
- infiltrative
- nodular
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what is Rx for each type of BCC?
- superficial: can do just topical creams
- infiltrative and nodular must excise
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what are the 2 main autoimmune bullous disease? and difference between 2?
- pemphigus vulgaris: more superficial. intraepidermal split
- bullous pemphigoid: deeper. subepidermal split. get tense blisters
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what investigation needs to be done for blistering conditions?
immunofluorescence
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