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SUGER > Physiology Of The Skin > Flashcards

Physiology Of The Skin Flashcards

1
Q

What is the largest organ of the body

A

Skin

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2
Q

What are the 3 layers of the skin

A

Epidermis
Dermis
Subcutis

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3
Q

What are the functions of the skin

A

Waterproof barrier
Physical barrier
Vitamin D synthesis
Endocrine organ
UV barrier
Barrier to infection
Immune organ
Sensory organ
Thermoregulation
Energy store
Shock absorber

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4
Q

What allows the skin to act as a waterproof barrier

A

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

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5
Q

What does the skin as a waterproof barrier prevent

A

It prevents transepidermal water loss

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6
Q

What functions does the epidermis have

A

Waterproofing
Physical barrier
Immune function
Vitamin D synthesis
UV protection
Thermoregulation

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7
Q

What functions does the dermis have

A

Thermoregulation
Vitamin D synthesis
Sensory organ

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8
Q

What functions does the subcutis have

A

Thermoregulation
Energy store/reserve
Vitamin D storage
Endocrine organ
Shock absorber

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9
Q

Why does skin wrinkle when wet

A

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

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10
Q

What causes washer woman syndrome

A

Due to water logging/ deceased person found in a wet environment

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11
Q

How does skin act as a physical barrier

A

Stratified epithelium helps to resist abrasive forces
Fat in the subcutis acts as a shock absorber

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12
Q

How is vitamin D synthesised and stored

A

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

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13
Q

Where can you get vitamin D2 and D3 from

A

Dietary intake
D3 = fish and meat
Vitamin D2 = supplements

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14
Q

What is the function of vitamin D

A

Absorbs calcium from the gut

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15
Q

What hormones act on the skin

A

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

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16
Q

What does skin colour depend on

A

Melanin
Carotenoids
Oxy/deoxyhaemoglobin

17
Q

How can UV-A and UV-B damage skin

A

Burns
Suppress action of langerhans cells
Photo-aging
DNA damage (skin cancers)

18
Q

Where is melanin synthesised

A

In melanosomes with melanocytes from tyrosine

19
Q

How is melanin transported

A

Via dendrites

20
Q

Where are carotenoids found

A

In brightly coloured vegetables

21
Q

What are the 2 types of melanin

A

Pheomelanin (red/yellow)
Eumerlanin (brown/black)

22
Q

Which is more abundant in the skin pheomelanin or eumelanin

A

All skin types contain more eumelanin than pheomelanin

23
Q

What does pheomelanin break down products increase the release of

A

Histamine release

24
Q

How does the skin respond to sunlight (stages)

A

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

25
Q

Describe the Fitzpatrick skin types

A

Skin type 1- very fair always burn never tan - Celtic
Skin type 2- fair, burn tan with difficulty - Scandinavian
Skin type 3- fair, burns but tans gradually- Caucasian
Skin type 4- medium, Harley burns tan with ease- Mediterranean
Skin type 5- light brown, rare to burn, tans well- Indian
Skin type 6- dark brown, never burns deeply pigmented- African

26
Q

How is the skin a barrier to infection

A

Peptides which are synthesised by granular layer keratinocytes have antimicrobial properties

27
Q

Where are Merkle cells found and what is there function

A

Basal epidermis
Function= light touch

28
Q

Where are encapsulated mechanoreceptors located, what are the 2 main types and what are there functions

A

They are found in the dermis
Pacinian corpuscles- function pressure/vibration
Meissner corpuscles- function touch

29
Q

Where are myelinated and unmyelinated sensory nerve endings found and what is there function

A

They are found in the dermis
Function- pain, itch, temperature

30
Q

How does skin regulate body temperature

A

It has subcutaneous fat which allows for insulation
It has cutaneous blood flow, eccrine sweating and hair for hair loss to reduce body temperature

31
Q

What does evaporation depend on

A

Surface area exposed
Temp and relative humidity of ambient air
Convective air currents

32
Q

What innervation does hairy skin have

A

Sympathetic alpha-noradregenic and sympathetic cholonergic

33
Q

What innervation does hairless skin have

A

Hairless skin only has sympathetic alpha-noradrenergic innervation

34
Q

What is a major limiting factor for sweating

A

Availability of water

35
Q

What is piloerection

A

Goosebumps

36
Q

What causes goosebumps

A

Arrector pili muscles innervated by the sympathetic alpha1-adrenergic fibres cause the rasing of cutaneous hairs

37
Q

What does subcutaneous fat act as

A

Insulator
Shock absorber
Energy store

38
Q

Why is skin an energy store

A

Skin has subcutaneous fat which contains white adipose connective tissue where energy can be stored

SUGER (17 decks)

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