Skin Function and Acne

Question 1

What are the three main functions of the skin?

Answer 1

Protection
Regulation
Sensation

Question 2

Describe how the skin acts as the primary function barrier

Answer 2

Mechanical impacts
Protects and detects pressure
Detects variations in temperature
Barrier to micro-organisms
Barrier to radiation and chemicals

Question 3

How does the skin regulate physiological processes?

Answer 3

Body temperature via sweat and hair
Changes in peripheral circulation
Fluid balance via sweat
Synthesis of vitamin D

Question 4

What are the four layers of the epidermis?

Answer 4

Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale

Question 5

Which one of the germ layers does the skin arise from?

Answer 5

Ectoderm

Question 6

Describe the embryology of skin?

Answer 6

Epidermis is derived from the ectoderm
5th week - the skin of the embryo is covered by simple cuboidal epithelium
7th week - single squamous layer (periderm) and a basal layer
4th month - an intermediate layer, containing several cell layers is interposed between the basal cells and the periderm
Early fetal period - the epidermis invaded by melanoblasts, cells of the neural crest origins
Hair - 3rd month as an epidermal proliferation into dermis
Cells of the epithelial root sheath proliferate to form a sebaceous gland bud. Sweat glands develop as downgrowths of epithelial cords into dermis

Question 7

Describe the immune system of the skin.

Answer 7

Langerhans cells (LC) are members of the dendritic cells family, residing in the basal layers

• specialises in antigen presentation, acquires antigens in the peripheral tissues, transports them to regional lymph nodes, presents to naive T-cells and initiate adaptive immune response
• activated T cells initiate cytokine release cascade

Question 8

Briefly describe the pathogenesis of skin allergy.

Answer 8

Skin irritation induces Langerhans cell migration and maturation

• migrate from epidermis to draining lymph nodes
• initial sensitisation takes 10-14 days from exposure to allergen
• once sensitised, contact dermatitis can develop within hours of repeat exposure

Question 9

What are the two categories of UV light onto skin?

Answer 9

Direct effects

Alterations in immunological function

Question 10

What are the direct effects of UV on skin?

Answer 10

Photoaging, DNA damage and carcinogenesis

Question 11

Describe the immunological effects UV light has on skin.

Answer 11

DNA damage can cause P53 tumour suppressor gene mutation (implicated in development of skin cancer)

Question 12

What are the effects of chronic UV exposure on skin?

Answer 12

Loss of elasticity
Fragility
Abnormal pigmentation
Haemorrhage of blood vessels
Premature ageing
Wrinkles

Question 13

What cells function to protect the skin from UV damage?

Answer 13

Keratinocytes and melanocytes

- work together to protect cells from UV DNA damage

Question 14

Briefly describe the relationship between vitamin D and the skin.

Answer 14

During exposure to sunlight, solar UVB photons are absorbed by 7-dehydrocholesterol in the skin and converted to previtamin D3
Pre-vitamin D3 undergoes transformation within the plasma membrane to active vitamin D3

Question 15

What is the most common cause of vitamin D deficiency in the UK?

Answer 15

During our winter there is minimal pre-vitamin D3 production in the skin, and few foods naturally contain vitamin D

Question 16

What are the risks of vitamin D deficiency?

Answer 16

Increased risk of common cancers, autoimmune diseases, infectious diseases and cardiovascular disease

Question 17

What are the types of encapsulated nerve endings in the skin?

Answer 17

Merkel cells
Meissner corpuscles
Ruffini’s corpuscles
Pacinian corpuscles

Question 18

What do Merkel cells at the base of the epidermis detect?

Answer 18

Respond to sustained gentle and localised pressure

Question 19

What do Meissner corpuscles (found directly below the epidermis) detect?

Answer 19

Very sensitive to light touch

- found the most on the palmar surfaces of the fingers and lips

Question 20

What do Ruffini’s corpuscles (found in the dermis) detect?

Answer 20

Sensitive to deep pressure and stretching

Question 21

What do Pacinian corpuscles (found deep in the dermis) detect?

Answer 21

These are mechanoreceptors which are sensitive only to deep touch
- present in high numbers around joints for proprioception

Question 22

Describe the pathophysiology of acne.

Answer 22

Sludging of sebaceous oils and accumulation of loose epithelial cells causes blockage of the follicular canal
Continued, thicker oil production and bacterial growth in the obstructive follicle causes rupture of the wall of the sebaceous gland and mild inflammation
As the proprionin bacteria spreads, marked inflammation occurs, and an inflamed lesion forms

Question 23

Name some possible clinical features of acne.

Answer 23

Papules
Pustules
Erythema 
Comedones (white/black heads)
Nodules
Cysts
Scarring

Question 24

What are some of the places acne can be found?

Answer 24

Face - easiest to treat
Chest
Back/shoulders
Occasionally found on the legs and scalp

Question 25

Name some of the subtypes of acne.

Answer 25

Papulopustular (most common)
Nodulocystic
Comedonal 
Steriod induced
Acne fulminans (acute, sudden onset, temperature and inflammatory makers)
Acne agminata - red, brown lumps and the face (eyelids, forehead, cheeks, chin and armpit)
Acne rosacea - red face
Acne inversus - in dark, moist places

Question 26

How is acne vulgaris treated?

Answer 26

Reduce plugging
- topical retinoid (benzoyl peroxidase)
Reduce bacteria
- topical antibiotics (erthromycin, clindamycin)
- oral antibiotics (tetracylines, erythromycin)
Reduce sebum production
- hormones - anti androgen (Dianette/OCP)
Oral isotretinoin

Question 27

What are some of the side effects of acne treatment?

Answer 27

Topical agents may cause irritation, burning, peeling and can bleach clothes
Oral antibiotics can cause GI upset
OCP carries risk of DVT

Question 28

What is the function of oral isotretinoin?

Answer 28

Oral retinoid for severe acne vulgaris
- contains concentrated vitamin A
16 week course at 1mg/kg
Acne remission in 80% of teenagers

Question 29

What are the side effects of oral isotretinoin?

Answer 29

Dry lips, nose blleds, dry skin and myalgia
Deranged liver function, rasied lipids, mood disturbance and teratogenicity
- women have to take a pregnancy test every 4 weeks and use two forms of protectin