Skin - Effect Of Environment On Skin Flashcards
Give reasons to why the skin is important
- The skin is a vital organ
- Normal adaptations of the skin to environmental pressures
- Abnormal effects of the environment such as:
- Physical damage to skin, nails and hair
- Ultraviolet damage: Burns, ageing and skin lesions
- Irritants, allergies and dermatitis
- Cutaneous infections
What is the integument?
- The interface between the body and the environment
- Thus subject to a wide range of insults
What May happen to the skin with extensive epidermal damage with severe burns? (Environmental insults on the skin)
Death May occur owing to one or more of
- Dehydration and shock
- Infection
- Heat loss and hypothermia
- Other factors such as protein loss, renal failure, electrolyte imbalance
State one type of fatal skin disease
- Toxic epidermal necrolysis: a rare adverse drug reaction
- Detachment of the epidermis
List the different environmental insults on the skin
- Irradiation & UV light
- Allergen
- Irritant
- Microbes, parasites
- Physical trauma (Burns, friction, pressure)
List some of the protective features of the skin
- Drying: Waterproof epidermis + oil from sebaceous glands
- Friction, impact: Thick regenerating epidermis, Nails
- Heat: Sweating, Vasodilation
- Cold: Subcutaneous fat, adaptable blood supply, hair
- Burns, Injury: Thick regenerating epidermis
- Radiation/sunlight: Thick epidermis, melanin
- Infections: Impervious epidermis
List some normal skin adaptations
- Sweating & Vasodilation in heat: Vasoconstriction in cold (Quite fast - Minutes)
- Tanning: Melanocyte response after ultraviolet exposure (Quite slow - Days)
- Hyperkeratosis: Thickening of stratum Corneum with rubbing or pressure after ultraviolet exposure (Quite slow - Days)
Describe how thermoregulation Is controlled by blood supply
- Arteriovenous (AV) shunts are anastomoses between arteriolars and venules
- Numerous in dermis
- Respond to thermoreceptors in the skin: Hot/Cold
When do the shunts open and close during thermoregulation of the blood supply
- Shunts open in response to decrease of blood flow to the superficial vascular plexus min the papillary dermis
- Shunts close in response to increase of blood flow to the superficial vascular plexus min the papillary dermis
- In face: Can also respond to emotion/sympathetic nervous system (blushing)
What happens if the arteriovenous shunts are shut off for too long?
Danger of damage (Frostbite’s May occur)
What is used to determine the colour of our skin?
- Dark skin is mainly due to melanin
- Light skin is mainly due to Haemoglobin
- There is a normal amount of genetic variation in the amount of melanin (<12 genes)
What does Melanin do in the skin?
- Protects against DNA damage and therefore against skin cancers
- Especially in dark (black & asiatic) skin
- Incidence is only 8-10% of that of white people
What happens during UV protection?
- The transfer of melanosomes (pigment granules) mainly to basal keratinocytes
What does Melanocytes do in terms of tanning?
- Melanocytes increase activity
- Make and transmit more Melanin
- Gives some protection against UV
- Additional protection by skin thickening in response to UV light
What is the process of suntanning?
Tyrosine -> L DOPA (via TYR) -> Dopaquinone (via TYR) -> either Eumelanins (brown to black) or Pheomelanins (yellow to red) via TRP’s
TYR = Tyrosinase TRPs = Tyrosine related proteins
What are langerhans cells?
What is the use of Langerhans cells in the body?
- Small cells in the non basal layer of the skin
- Protection against Microorganisms
What is the function of langerhans cells?
- They’re antigen presenting cells
- Form a network in the epidermis which is a part of the immune system
List some abnormal effects of the environment
- Friction-scratching
- Ultraviolet irradiation
- Burns
- Irritants
- Allergens
- Microbes (Bacteria, Viruses and fungi)
What is lichenification?
- A more extreme form of hyperkeratosis
- A Reaction to excessive rubbing or scratching
Why is the Ozone layer useful?
- Helps block out UV light from entering the earths atmosphere and damaging the skin
- Blocks UVC, some UVA and UVB
What is sunburn caused by?
How can it be treated?
- Caused by UV irradiation
- It is a radiation burn
- Causes Blisters, inflammation and cell death
- Associates with increased risk of cancer
- Even if you’ve used a radiation bed below age 35 by 75%
What are Naevi? (Moles)
- benign proliferation of melanocytes
- Many or large naevi are risk factors for melanoma skin cancers
What are freckles? (Ephelides)
- Involve a genetic component
- Linked to either Red or Fair hair
- Often linked to MC1R gene variants
- Affects areas exposed to the sun
List the different skin related diseases caused by UV radiation
- Sunburn
- Polymorphic light eruption
- Wrinkles: Solar elastosis (Loss of elasticity)
- Naevi (moles)
- Freckles (ephelides)
- Solar lentigos [liver spots, age spots]
- Solar keratoses
- Basal cell carcinoma
- Melanoma
What is special about a basal cell carcinoma?
- Often curable by surgery
- especially if reported early!
What is a melanoma?
- Caused by UV radiation
- Can be thin but is still dangerous
- Spread rapidly
What are the benefits of UV light?
- UV is needed for vitamin D3 production in skin
- 15 minutes of summer sun on face & arms per day is enough for white skin
- Longer for dark skin or take tablets
- Ultraviolet radiotherapy for skin conditions
What are the different types of skin burns?
1st degree burns: Burns up to the epidermis
2nd degree burns: Burns past the epidermis and half way through the dermis (May not scar)
3rd degree burns: Burns through the epidermis, dermis and to the fat in the skin. (Leaves scarring)
How do irritants contact dermatitis?
- Occurs when there’s too much exposure to a substance
- Can still use it, but reduce amount
- People vary in sensitivity
- Any of redness, itching, swelling, blistering and/or scaling
How do allergens contact dermatitis?
- Allergy to something that contacts skin, immune system involved
- Tiny amounts may be sufficient
- Varies greatly between people, may develop after long or short use
- Any of: Redness, itching, swelling, blistering and/or weeping
- Avoid allergen in future
Comment on how common/uncommon irritants or allergic contact dermatitis’s are
- Irritant contact dermatitis is common
- Allergic contact dermatitis is relatively uncommon
- Sensitisation first: Langerhans cells process antigen and present to lymphocytes
- Delayed hypersensitivity occurs at next exposure (memory T cells)
List the different types of microbes
- Paronychia
- Fungal: Tinea capitis
- Bacterial impetigo
- Bacterial cellulitis
- Virus: Human papilloma virus (HPV)
Describe how an infection works
- Portal of entry: Microbes can enter breach in epidermis
- Impaired immunity predisposes to infection such as:
- HIV and viral warts
- Eczema herpeticum, which is herpes (cold sore) virus infecting eczema
Conclude the skin as a whole
The skin is a vital organ with normal adaptive mechanisms to: temperature changes (sweating, vasodilation & vasoconstriction), friction (hyperkeratosis) and UV radiation (melanin production).
