Effect Of Environment On Skin Flashcards
What is toxic epidermal necrolysis?
→ Detachment of the epidermis that is fatal
What are environmental insults?
→ UV light
→ Physical trauma
→ Microbes
→ Allergens
→ irritants
What are fast adaptations of the skin?
→ Sweating and vasodilation in the heat
→ Vasoconstriction in the cold
What are two slow adaptations of the skin?
→ Hyperkeratosis : thickening of the stratum corneum with rubbing or pressure
→ Melanocytes : tanning
What are AV shunts?
→ Anastomoses between arterioles and venules
What do AV shunts respond to?
→ thermoreceptors in the skin
What do AV shunts do?
→ Open and close to increase or decrease blood flow to the superficial vascular plexus in the papillary dermis
What can AV shunts in the face do?
→ Respond to emotion
→ blushing
What happens if AV shunts are shut off for too long?
→ danger of damage (frostbite)
What is the color of human skin due to?
→ Melanin and haemoglobin
What does melanin do?
→ protect against DNA damage and skin cancer
Where do melanosomes get transferred to?
→ basal keratinocytes
What happens to melanocytes during tanning?
→Melanocytes increase activity
→ They make and transmit more melanin
What 2 things happen to protect against UV?
→ Tanning
→ Skin thickening (Slowly)
Describe the process of tanning
→ UV light shines on keratinocytes and damages the DNA if there isn’t enough melanin
→ MSH gets produced by the keratinocytes
→ MSH binds to its receptor MC1R
→ It signals the cAMP pathway
→ More melanin is produced
→ Melanosomes go into the keratinocytes and build up the cap
What is tanning set off by?
→ DNA damage
Where are Langerhans cells found?
→ In the non basal layers of the skin
What is the function of Langerhans cells?
→ Antigen presenting cells
→ form a network in the epidermis
What is lichenification and how does this occur?
→ more extreme hyperkeratosis
→ Reaction to excessive rubbing or scratching
What are the 3 types of UV rays?
→ UVA and UVB (hit earth)
→ UVC (stopped by ozone)
What type of burn is sunburn?
→ A radiation burn
What happens during sunburn?
→ Blisters
→ Inflammation
→ Cell death
What is sunburn associated with?
→ Risk of cancer
→solar elastosis
What is a polymorphic light eruption?
→ Being allergic to sunlight
→ Rash when out in the sun
What are naevi?
→ a benign proliferation of melanocytes
What do many naevi mean?
→ Risk factor for melanoma, skin cancer
What are freckles linked to?
→ Red/fair hair
→ MC1R gene variants
What are solar lentigos?
→ Liver/Age spots
What are solar keratoses?
→ Dysplastic growth of keratinocytes
What cells does melanoma affect?
→ melanocytes
What cells does non-melanoma affect?
→ keratinocytes
What are the two types of non-melanoma cancers?
→ Squamous cell carcinoma
→ Basal cell carcinoma
What are the characteristics of basal cell carcinoma?
→ It doesn’t spread easily
→ Often curable by surgery
What is UV needed for?
→ Vitamin D3 production in the skin
What are the three types of burn?
→ Superficial
→ Partial thickness- some sacrring
→ Full thickness- loss of pinprick sensation, scarring
When does irritant contact dermatitis occur?
→ Too much exposure to a substance
What are the symptoms of irritant contact dermatitis?
→ Redness, itching, swelling, blistering
What is allergic contact dermatitis?
→ Allergy to something that contacts the skin
→ Small amount is sufficient
What are the steps to allergic contact dermatitis?
→ Sensitisation first : Langerhans cells process antigen and present it to the lymphocytes
→ Delayed hypersensitivity occurs at the next exposure
What is paronychia?
→ Nail fold infection
→ Can be fungal or bacterial
What is tinea capitis?
→ Scalp ringworm
What is impetigo?
→ an injury getting infected
Where can microbes enter?
→ In a breach in the epidermis
What does the AV shunt do in hot temperatures?
→Shunt is closed allowing continuous blood supply through arterioles to subpapillary plexus
What does the AV shunt do in cold temperatures?
→Shunts open. Blood is shunted straight to venous so blood id not taking through arterioles to the skin
Summarise molecular cascade of suntanning
→Tyrosine →L-DOPA →DOPAquinone →TRPs →Eumelanin or pheomelanin
What bacteria is responsible for cellulitis?
→streptococcus
What virus is responsible for warts?
HPV
