Effect of the environment on the skin Flashcards
What is the integuement?
the interface between the body and the environment
Why may death occur if the skin is damaged in burns/rare drug reaction
- dehydration
- shock
- infection
- heat loss / hypothermia
What is toxic epidermal necrolysis?
- rare adverse drug reaction
- detachment of epidermis
- often fatal
What are some environmental insults to the skin?
- irradiation/uv light
- microbes
- burns/friction
- irritants
- allergens
What are some adaptations of skin in response to the environment?
- sweating/vasodilation in heat
- vasoconstriction in cold
What is hyperkeratosis?
- thickening of the stratum corneum with rubbing or pressure or after uv exposure
- takes weeks
What are AV shunts?
- anastomoses between arterioles and venules
- found in dermis
- respond to thermoreceptors in skin
- if open, sub-papillary plexus gets less blood and vice versa
- shunts open or close respectively to increase or decrease blood flow to the superficial vascular plexus in the papillary dermis (just below the epidermis)
- can respond to emotion in face, causing blushing
- if shut for too long there is danger of frostbite
What does melanin do?
- protects against DNA damage and thus skin cancer
- sets the colour of human skin in black people (haemoglobin does it in white people)
How does tanning wok?
There is a basal keratinocyte and a melanocyte with some processes.
It sends these melanosomes in the keratinocyte.
There is a basal level of pigment synthesis, so there is a little bit of melanin all the time there, but when the sun shines, we get DNA damage in the keratinocyte, which makes it produce molecules.
The molecules result in this keratinocyte making a hormone called MSH (melanocyte-stimulating-hormone). Melanocytes have a receptor called MC1R (melanocortin 1 receptor). So if they see some MSH they become stimulated through a cyclic AMP pathway. More transcription of specialised genes, so basically it makes more melanin and transfers more to the keratinocyte.
How does skin protect against micro-organisms?
has:
- Langerhans cells
- small cells in non-basal layers of skin
- dendritic cells
- apcs form a network in the epidermis
What is lichenification?
a more extreme form of hyperkeratosis
reaction to excessive rubbing or scratching/skin conditions
What are some types of skin damage we can get by UV radiation?
1) Sunburn
- It is a radiation burn
- Blisters, inflammation, and cell death (severe DNA damage)
- Ever sunburnt, associates with increased risk of skin cancer
- So does ‘ever used a UV sunbed below age 35’ by 75%
2) Polymorphic light eruption
- Sun allergy
- You get a rash if you have too much sun
3) Wrinkles - solar elastosis (loss of elasticity)
- Loss of elastic fibres due to sun damage
4) Naevi (moles)
- You can be born with moles but most of them come with sun exposure
- Singular word for mole is a naevus
- Benign proliferation of melanocytes
- If you have a lot of naevi/extra large one, that is a risk factor for melanoma skin cancer
5) Freckles (ephelides)
- Involve a genetic component
- Also linked to red/fair hair
- Often MC1R gene variants
- Happen in sun-exposed areas
- Solar lentigos = liver spots, age spots. Common on the hands in older people
6) Solar keratoses
- Dysplastic growth of keratinocytes
- A sort of benign growth of keratinocytes
- Caused by proliferation of the keratinocytes which stops
- Common on the top of the head in bald people
What are the two types of skin cancer?
- melanoma (melanocytes) (most dangerous)
- non-melanoma (mostly keratinocytes) split into squamous cell carcinoma and basal cell carcinoma
What are the signs of basal cell carcinoma?
- dark coloured ulcer
- curable by surgery, especially the earlier it is reported
What is melanoma?
- can be thin but still dangerous because it spreads rapidly
- caused by UVA and UVB rays
