Physiology Of The Skin Flashcards
What is the largest organ of the body
Skin
What are the 3 layers of the skin
Epidermis
Dermis
Subcutis
What are the functions of the skin
Waterproof barrier
Physical barrier
Vitamin D synthesis
Endocrine organ
UV barrier
Barrier to infection
Immune organ
Sensory organ
Thermoregulation
Energy store
Shock absorber
What allows the skin to act as a waterproof barrier
Tight junctions between the cells in the stratum granulosum, epidermal lipids and keratin in stratum corneum which forms an inside-out and outside-in barrier to water
What does the skin as a waterproof barrier prevent
It prevents transepidermal water loss
What functions does the epidermis have
Waterproofing
Physical barrier
Immune function
Vitamin D synthesis
UV protection
Thermoregulation
What functions does the dermis have
Thermoregulation
Vitamin D synthesis
Sensory organ
What functions does the subcutis have
Thermoregulation
Energy store/reserve
Vitamin D storage
Endocrine organ
Shock absorber
Why does skin wrinkle when wet
Skin on fingers and toes will wrinkle after been immersed for longer than 5 mins which is mediated by sympathetic nervous system due to the vasoconstriction in the dermis which changes the amount of fluid in the dermis which improved the grip
What causes washer woman syndrome
Due to water logging/ deceased person found in a wet environment
How does skin act as a physical barrier
Stratified epithelium helps to resist abrasive forces
Fat in the subcutis acts as a shock absorber
How is vitamin D synthesised and stored
UV rays from the sun are absorbed by the skin by 7-dehydrocholestrol in the plasma membrane of epidermal keratinocytes and dermal fibroblasts and converts it into pre vitamin D3 this is then synthesised in the liver to 25-hydroxyvitamin D3 which is then converted in the kidney to become 1,25-dihydroxyvitamin D3 which is stored in the adipocytes in the subcutis layer of the skin
Where can you get vitamin D2 and D3 from
Dietary intake
D3 = fish and meat
Vitamin D2 = supplements
What is the function of vitamin D
Absorbs calcium from the gut
What hormones act on the skin
Androgens (testosterone)- these act on follicles and sebaceous glands (greasy skin/hair)
Thyroid hormones(thyroxin)- these act on keratinocytes, follicles, dermal fibroblasts, sebaceous glands, eccrine glands- low thyroxin levels can cause thicken skin, scaly/dry skin, brittle hair and nails, decreased sweating
What does skin colour depend on
Melanin
Carotenoids
Oxy/deoxyhaemoglobin
How can UV-A and UV-B damage skin
Burns
Suppress action of langerhans cells
Photo-aging
DNA damage (skin cancers)
Where is melanin synthesised
In melanosomes with melanocytes from tyrosine
How is melanin transported
Via dendrites
Where are carotenoids found
In brightly coloured vegetables
What are the 2 types of melanin
Pheomelanin (red/yellow)
Eumerlanin (brown/black)
Which is more abundant in the skin pheomelanin or eumelanin
All skin types contain more eumelanin than pheomelanin
What does pheomelanin break down products increase the release of
Histamine release
How does the skin respond to sunlight (stages)
Immediate pigment darkening- occurs within minutes and lasts hours/days
Persistent pigment darkening- occurs within hours and lasts 3-5 days
Delayed tanning- occurs after 2-3 days of UV exposure can last between 10-28 days
