Effects of the environment on the skin

Question 1

Describe some fast and slow adaptations of the skin

Answer 1

• Sweating and vasodilation in the head, vasoconstriction in the cold = Quite fast (minutes) - Hyperkeratosis (callus): thickening of the stratum corneum with rubbing or pressure (e.g heel of foot or guitarist fingers) = Slow (weeks) - Melanocytes: tanning after ultraviolet exposure = Slow (days)

Question 2

What are AV shunts?

Answer 2

AV shunts are anastomoses between arterioles and venules

Question 3

What do AV shunts respond to?

Answer 3

Respond to thermoreceptors in skin

Question 4

What do AV shunts do?

Answer 4

AV shunts open and close to increase or decrease blood flow to the superficial vascular plexus in the papillary dermis

AV shunt closed = increase blood supply to superficial vascular papillary plexus = skin goes redder = more heat loss

AV shunt open = decrease superficial blood supply to superficial vascular plexus in the papillary dermis, skin goes blue = less heat loss

Question 5

What do AV shunts in the face respond to?

Answer 5

Respond to emotion

Question 6

What happens if the AV shunts shunt off for too long?

Answer 6

If the AV shunts shut off for too long there’s danger of frostbite

Question 7

What is the colour of skin mainly due to?

Answer 7

Mainly due to melanin and haemoglobin

Question 8

What does melanin protect against?

Answer 8

Melanin protects against DNA damage and thus skin cancer

Question 9

What happens to melanocyte activity in tanning?

Answer 9

Melanocytes increase activity-make and transmit more melanin

Question 10

Steps involved in the basics of suntanning?

Answer 10

-UV light shines on the keratinocyte and damage DNA if there isn’t enough melanin -This results in the production of MSH by keratinocyte -MSH binds to MC1R on melanocyte causing cAMP signalling resulting in: -Increased melanin synthesis and transfer -Increased cell division

Question 11

What is lichenification?

Answer 11

More extreme form of hyperkeratosis

Question 12

What is toxic epidermal necrolysis

Answer 12

Rare adverse drug reaction resulting in detachment of the epidermis which can be fatal

Question 13

What features of the skin protect from various stresses?

Answer 13

• Drying: Waterproof epidermis + oil from sebaceous glands • Friction, impact: • Thick, regenerating epidermis; keratin • Nails • Basement membrane anchoring epidermis to dermis, wavy border against shear forces • Collagen fibres in dermis (strong, running in all directions) • Heat: Sweating; vasodilatation • Cold: Subcutaneous fat, adaptable blood supply, hair (head) • Burns, injury: Thick, regenerating epidermis • Radiation/sunlight: thick epidermis; melanin • Infections: Impervious epidermis; resident cells of immune system

Question 14

How can the skin become damaged by ultraviolet radiation?

Answer 14

There are three bands of ultraviolet radiation UV A, B and C.

Band UV A is the longest and UV C is the shortest.

These are all shorter than visible light.

Question 15

Sunburn

Answer 15

Radiation burn caused by DNA damage

Results in bilsters, inflammation and cell death

Being sunburnt associates with an increased risk of cancer

Using a sunbed below the age of 35 - increases the risk of skin cancer by 75%

Question 16

What is polymorphic light eruption?

Answer 16

When people are sensitive to sunlight resulting them to develop a rash which appears as red tiny bumps or slightly raised patches.

Question 17

Naevi

Answer 17

Naevi are moles (singular - Naevus)

Naevi occur due to benign proliferation of melanocytes.

Many or large naevi are a risk factor for melanoma skin cancer.

Question 18

Freckles

Answer 18

Involve a genetic component

Freckles linked to variants of the MC1R gene, mutant MSH receptor = not very good at suntanning.

Freckles occur in sun-exposed areas

Question 19

Solar Lentigos

Answer 19

Liver spots, age spots

Question 20

Solar Keratoses

Answer 20

• Dysplastic growth of ketatinocytes (benign proliferative growth)
• Caused by UV damage
• Common on the head in bald people

Question 21

What are the types of skin cancer?

Answer 21

Melanoma (most dangerous)

Non-melanoma - mostly keratinocytes = most common

Non melanoma split into squamous cell carcinoma and basal cell carcinoma

Question 22

What is a basal cell carcinoma?

Answer 22

• Most common
• Often curable by surgery if reported early
• Dark coloured ulcer present in old people can often be a sign of basal cell carcinoma
• Is curable

Question 23

What is a Melanoma?

Answer 23

Can be thin but still dangerous, spreads rapidly

UVB aswell as UVA can cause melanomas in pigmented mice (relevant to sunscreen design and tanning salon)

Question 24

What is the good side of UV?

Answer 24

UV is needed for vitamin D production in the skin.

Ultraviolet radiotherapy for skin conditions e.g vitiligo, psoriasis (patchy loss of pigment)

Question 25

Irritant Contact Dermatitis

Answer 25

Skin becomes irritated (dermatitis) due to prolonged exposure to a substance. * You are still able to use it but in varied amounts * People vary in sensitivity * Any of: Redness, itching, swelling, blistering and/or scaling

Question 26

Allergic Contact Dermatitis

Answer 26

- Allergic to something that contacts the skin - immune system involved - Tiny amount may be enough - Varies greatly between people. May develop after long or short use. - Any of: Redness, itching, swelling, blistering and/or weeping Allergen should be avoided in the future e.g rash to gold necklace

Question 27

What are the steps involved in the development of a skin allergy

Answer 27

1. **Sensitization first:** Langerhans cells process antigen and ‘present’ to lymphocytes 2**. Delayed hypersensitivity** occurs at next exposure and produce an allergic response (memory T-cells)

Question 28

What is paronychia?

Answer 28

Nail fold infection - can be bacterial or fungal

Question 29

What is tinea capitis?

Answer 29

Scalp ringworm (fungal example) - Mild case can be source of dandruff, severe case is patchy loss of hair

Question 30

Give two examples of microbial skin diseases?

Answer 30

**Impetigo** **Cellulitis, often caused by Streptococcus (bacterial example)** Occurs when the lymphatics become infected with bacteria, there is a risk where the bacteria can get into the blood stream

Question 31

What is human papilloma virus (HPV)?

Answer 31

Warts People with HIV can get a worse case of HPV as their immune system is deficient. Humans with a normal functioning immune system will readily control the warts virus, HIV sufferers will have an extreme case

Question 32

How can microbes enter the skin?

Answer 32

**_- Portal of entry:_** microbes can enter breach in epidermis **_- Impaired immunity predisposes to infection,_** e.g. HIV and viral warts; eczema herpeticum, which is herpes (cold sore) virus infecting eczema | (e.g. Streptococcus in cellulitis)