Lecture 23B - Skin Damage

Question 1

Damage to the skin?

Answer 1

adverse drug reactions

allergic reactions, contact with chemicals

wounds and wound healing

sunburn and melanoma

disturbance of the microbiota and infection

Question 2

What are the 4 stages of wound healing?

Answer 2

hemostasis

inflammation

proliferation

remodelling

Question 3

What can penetrate the external layer of the skin?

Answer 3

cuts, penetration of thorns or other sharps and injuries can penetrate through the skin layers right down to vital organs below

Question 4

Wha does haemostasis involve?

Answer 4

stopping the bleeding by clot formation

Question 5

What is released in haemostasis?

Answer 5

histamine from mast cells which causes vasoconstriction as well as changing permeability of the blood vessel wall

Question 6

What do neutrophils and macrophages do in haemostasis?

Answer 6

enter the damaged area to help remove damaged cells and any bacteria/pathogens which have been introduced beneath the surface barrier of the skin

Question 7

What is the clot?

Answer 7

a temporary plug which fills the breach in the skin until it can be repaired

Question 8

What happens in inflammation?

Answer 8

in response to chemotactic factors, monocytes will migrate to the damaged tissue by diapedesis and differentiate into macrophages

Question 9

What do factors released from macrophages and neutrophils do?

Answer 9

cause more cells to be recruited to the site of injury and for specific aspects of immune system to be activated

Question 10

What does inflammatory factors and cytokines do?

Answer 10

cause the site to become hot and throbbing

Question 11

What is proliferation?

Answer 11

alongside the inflammatory response, cell proliferation responses begin to repair the damage

Question 12

What does a scab (eschar) do?

Answer 12

helps protect the underlying repair processes

Question 13

What do endothelial cells do?

Answer 13

proliferate as they repair blood vessels

Question 14

What do fibroblasts do?

Answer 14

help repair the connective tissue matrix as well as repairing the skin layer at the top itself

Question 15

What does closure of a cut involve?

Answer 15

myofibroblasts

Question 16

What do myofibroblasts do?

Answer 16

sit at the edge of an open cut and extend a podium forward as they migrate across the open space in the wound and form a continuous barrier

Question 17

What do their myofibrils do?

Answer 17

contract to pull the normal cells at the edge of the cut along behind them

Question 18

What does the action of fibroblasts do?

Answer 18

helps pull the two separate edges of the cut together till the epidermal layer becomes continuous again

Question 19

How long does complete remodelling take?

Answer 19

a few months for it to be as strong as it was before injury

continues for a long time after the surface has been resealed by the skin

Question 20

What are factors that can directly affect wound healing?

Answer 20

body site

infection

vascular supply

mechanical stress

desiccation

edema

Question 21

Factors which can indirectly affect wound healing?

Answer 21

age and nutrition, medication, alcoholism, drug abuse, hygiene

diabetes

autoimmune disease

venous stasis

predisposition to keloids

some genetic skin diseases

immunocompromised state

obesity, immobility, vaculitis, neuropathy

Question 22

What can compromise healing in some tissues?

Answer 22

medical conditions such as cardiovascular disease

Question 23

What does elasticity of skin change with?

Answer 23

age

Question 24

What does tanning involve?

Answer 24

p53 activation in keratinocytes in response to UVR-induced DNA damage

Question 25

What does p53 activation lead to?

Answer 25

p53 up-mediated regulation of proopiomelanocortin (POMC)

Question 26

What does posttranslational cleavage of POMC produce?

Answer 26

beta endorphin and alpha-MSH

Question 27

What does alpha-MSH do?

Answer 27

stimulates MC1R on adjacent melanocytes, resulting in melanin synthesis and eventual transfer of melanin-containing vesicles to keratinocytes (pigments) which causes a tan

Question 28

What are melanosomes?

Answer 28

melanin containing vesicles

Question 29

What does chronic UVR result in?

Answer 29

elevated circulating beta endorphin levels, leading to analgesia and a physical dependence on tanning

Question 30

What is MSH?

Answer 30

melanocyte stimulating hormone

Question 31

What ca overexposure to UV radiation induce?

Answer 31

skin cancer tanning does not eliminate the potential damage from overexposure to UV

Question 32

What are darker skin tones?

Answer 32

protective as skin cancer is much less common among African-Americans

Question 33

What are lighter skin tones better for?

Answer 33

vitamin D production, but more susceptible to DNA damage by strong sunlight

Question 34

What is non-melanoma cancer?

Answer 34

most commonly diagnosed cancer in Scotland it is readily treatable if detected early

Question 35

What does squamous cell carcinoma?

Answer 35

arises fro mature keratinocytes and can appear as recurrent open sore (bleeds)

Question 36

What is basal cel carcinoma?

Answer 36

arises in the germinal layer of keratinocytes and invades the tissue

Question 37

Where does melanoma occur?

Answer 37

in the melanocytes and is a more serious form of cancer which needs to be detected as early as possible to maximise the chance of successful treatment

Question 38

Types of non-melanoma skin cancer?

Answer 38

squamous cell carcinoma and basal cell carcinoma

Question 39

How many bacteria are there on our skin?

Answer 39

1 million bacteria per cm2

Question 40

What is the microbiota?

Answer 40

the microbial biocommunity of bacteria, viruses and fungi

Question 41

What do the bacteria on skin do?

Answer 41

protect the skin from colonisation of harmful bacteria and microbes - a sterile skin provides opportunities for pathogens to invade

Question 42

What is healthy skin home to?

Answer 42

trillions of bacteria, viruses and fungi

Question 43

What does genetic predisposition mean?

Answer 43

can make is easier for microbes to breach the skin barrier or make the skin more sensitive to their presence some peoples sin can be thinner and the protective barrier is weaker

Question 44

How can metabolic diseases affect the skin?

Answer 44

can alter the balance of nutrients on the skin and the vascular supply to the skin, leading to an increase in the density of microbes or a change in the relative proportions of their individual populations

Question 45

What can happen if the skin is breached by a wound?

Answer 45

members of the microbiota which are normally harmless on the skin surface could act as pathogens once they get access to the internal tissue

Question 46

What can happen once an infection of the skin takes route?

Answer 46

additional skin microbes may contribute to inflammatory processes which can themselves cause tissue damage

Question 47

How can treatments affect the skin?

Answer 47

e.g. topical steroids or environmental changes can change growth conditions for microbes and facilitate overgrowth of potentially harmful bacteria