MSS Effects of Environment of Skin Flashcards
Why is the skin a vital organ?
Death may occur following extensive skin damage, e.g. severe burns or a rare drug reaction.
This is through one or more of:
- Dehydration and shock
- Infection
- Heat loss and hypothermia (or hyperthermia due to impaired thermoregulation)
- Others: protein loss; electrolyte imbalance; high-output
cardiac failure; renal failure.
Describe the different types of environmental insults
Describe the basal features of intergument which protect the skin against various stresses
3 normal adaptations of skin to environmental stresses?
- Sweating and vasodilatation in heat; vasoconstriction in cold. quite fast (in minutes)
- Hyperkeratosis (callus) - thickening of stratus corneum with rubbing or pressure (e.g. feet, guitarist fingers), or (slighty) after UV exposure. slow (in weeks)
- Tanning (melanocyte response) - after UV exposure. quite slow (days)
Describe thermoregulation by skin’s blood supply
Thermo-receptors in skin control BF via symp nerves.
Vessel walls relax to increase arterial BF + heat loss (hot) or contract to decrease BF (cold) to the superficial (subpapillary) plexus below epidermis.
Hairless/glabrous skin (palms) also has AV shunts or anastomoses between arteries and a high-capacity venous plexus in the dermis. Shunts likewise open/close.
however if Reduce blood flow for too long –> frostbite to extremities.
Label this, what does it show?
Why do we get tanned upon sun exposure?
Melanocytes make more melanin y hay epidermal thickening to protect against more UV
DNA damage is the actual mechanism for sun-tanning, so tanning=you have significant DNA damage in your skin!
DNA damage signalling causes keratinocyte to make MSH - this activates MCR1 (melanocortin 1 receptor), stimulating melanocytes
Via their cAMP pathway, melanocytes increase melanin synthesis + transfer, and also cell division
More melanosomes goes to keratinocyte, arranged on top of nucleus–> increased protection against UV!
MCR1 gene is mutated in which types of ppl?
What does this show?
Differentiate between irritant and allergic contact dermatitis
Irritant contact dermatitis: common, upon too much
exposure to a substance. Reduce amount
Allergic contact dermatitis relatively uncommon
(e.g. nickel): immune mediated, tiny amount can be enough. Completley avoid amount
Sensitization first: Langerhans cells present Ag to lymphocytes. Delayed hypersensitivity (type IV) occurs at next exposure (memory T-cells)
Redness, itching, swelling, blistering, scaling or (weeping for allergic only) symptoms
These show examples of when mircobes infiltrate the skin. What do each of these show?
Microbes can enter a breach in the epidermis
e.g. streptococcus in cellulitis
Impetigo common in children, thinner skin
Also, impaired immunity predisposes to infection
- e.g. HIV and HPV viral warts
- eczema herpeticulum, which is herpes virus infecting eczema
Differentiate between 1st 2nd and 3rd degree burns
1st degree - superficial burn - affects just the epidermis
2nd degree affects some of the dermis, sebaceous glands still remaining, probs won’t scar
3rd degree is where most of dermis is lost including sense organs - loss of pinprick sensations
Give the types of UV radiation
UVA, UVB, UVC
- UVA has the longest UV wavelengths
- mainly UVA and some UVB reaches ground level
- ozone blocks some UVA and UVB/
Describe sunburn
A radiation burn
Inflammation can include blisters = epidermal cell death (severe DNA damage), or peeling (less severe damage)
‘Ever sunburnt’= increased skin cancer risk, so does ‘ever used a UV sun bed below 35’ - by 75%
Differentiate between naevi and freckles
Naevi: benign melanocyte proliferation. Many/large naevi = risk factor for melanoma
Freckles: aka ephelides, linked to red/fair hair
Often MC1R gene variants
Tend to be in sun exposed areas
Differentiate between solar lentigos and solar keratoses
Describe the classification of skin cancer
Divided into melanoma (melanocytes) and non-melanoma (mostly keratinocytes)
Melanoma is more dangerous
Non-melanoma can be divided further
- squamous cell carcinoma
- basal cell carcinoma (most common)
- other
