Effects of the environment on the skin Flashcards
What is the cell flow in the epidermis?
- Start in the basal layer - stem cells divide
- daughter cells move distally through the epidermis
- differentiate into mature keratinocytes - make keratin (tough, waterproof protein)
- Stratum corneum - cornified keratinocytes lose nuclei, continuing to move distally
What happens if you have severe epidermal damage? i.e. severe burns or drug reaction
- May die from:
- dehydration and shock
- infection
- heat loss and hypothermia
- hyperthermia from impaired thermoregulation
- protein loss, electrolyte imbalance, high-output cardiac failure, renal failure
How does the skin protect us?
- Drying - waterproof epidermis and oil from sebaceous glands
- Heat - sweating, vasodilation
- Cold - subcutaneous fat, adaptable blood supply, hair
- Burns/injury - thick, regenerating epidermis
- Radiation/sunlight - thick epidermis, melanin
Infections - resident immune cells - friction/impact - regenerating epidermis, keratin, nails, collagen in dermis, basement membrane anchoring epidermis to dermis (wavy border against shear forces)
Melanocytes
cells in basal epidermal layer with dendrites that feed pigment to keratinocytes
Tanning
- melanocytes increase activity - make and transmit more melanin
- caused by DNA damage by UV
- gives some protective from UV
What is Lichenification
- Extreme form of hyperkeratosis
- Reaction to excessive rubbing or scratching / skin condition
Name 5 effects of UV
- Tan
- Sun burn
- Polymorphic light eruption (allergy)
- Wrinkles - loss of elasticity
- Naevi (moles) - benign proliferation of melanocytes - many or large increase risk of melanoma
- Freckles
- Solar lentigos - liver spots/age spots
- Solar keratoses
What are the different types of skin cancer?
- Melanoma (melanocytes)
- Non-melanoma (keratinocytes) - squamous or basal cell carcinoma
What good effects does UV have?
- Converts 7-dehydrocholesterol into Vit D (which is then converted into the active 1,25-dihydroxyVit D)
- UV radiotherapy can be used for skin conditions such as vitiligo and psoriasis
Types of burn
- Superficial burn - destroys epidermis
- Deeper to sebaceous glands in dermis
- Deep burn - destroys both epidermis and dermis - will scar and may lose sensation of pinprick
What is irritant contact dermatitis?
- Common
- Occurs with too much exposure to a substance
- can still use it, but reduce amount
- people vary in sensitivity
- Redness, itchiness, swelling, blistering, scarring
What is allergic contact dermatitis?
- Relatively uncommon
- allergy to something that contacts skin
- tiny amount may be sufficient
- varies greatly between people
- Langerhans cells process antigen and present to lymphocytes. Delayed hypersensitivyt occurs at next exposure (memory T cells)
- redness, itching, swelling, blistering, weeping
Name two fungal skin infections
- Paronychia (nail fold infection - can also be bacterial)
- Tinea capitis (scalp ringworm)
Name two bacterial skin infections
Impetigo
Cellulitis - Streptococcus
Name a viral skin infection
Human papilloma virus (HPV) - warts
