Skin Function and Acne Flashcards
What are the three main functions of the skin?
Protection
Regulation
Sensation
Describe how the skin acts as the primary function barrier
Mechanical impacts Protects and detects pressure Detects variations in temperature Barrier to micro-organisms Barrier to radiation and chemicals
How does the skin regulate physiological processes?
Body temperature via sweat and hair
Changes in peripheral circulation
Fluid balance via sweat
Synthesis of vitamin D
What are the four layers of the epidermis?
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
Which one of the germ layers does the skin arise from?
Ectoderm
Describe the embryology of skin?
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
Describe the immune system of the skin.
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
Briefly describe the pathogenesis of skin allergy.
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
What are the two categories of UV light onto skin?
Direct effects
Alterations in immunological function
What are the direct effects of UV on skin?
Photoaging, DNA damage and carcinogenesis
Describe the immunological effects UV light has on skin.
DNA damage can cause P53 tumour suppressor gene mutation (implicated in development of skin cancer)
What are the effects of chronic UV exposure on skin?
Loss of elasticity Fragility Abnormal pigmentation Haemorrhage of blood vessels Premature ageing Wrinkles
What cells function to protect the skin from UV damage?
Keratinocytes and melanocytes
- work together to protect cells from UV DNA damage
Briefly describe the relationship between vitamin D and the skin.
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
What is the most common cause of vitamin D deficiency in the UK?
During our winter there is minimal pre-vitamin D3 production in the skin, and few foods naturally contain vitamin D
What are the risks of vitamin D deficiency?
Increased risk of common cancers, autoimmune diseases, infectious diseases and cardiovascular disease
What are the types of encapsulated nerve endings in the skin?
Merkel cells
Meissner corpuscles
Ruffini’s corpuscles
Pacinian corpuscles
What do Merkel cells at the base of the epidermis detect?
Respond to sustained gentle and localised pressure
What do Meissner corpuscles (found directly below the epidermis) detect?
Very sensitive to light touch
- found the most on the palmar surfaces of the fingers and lips
What do Ruffini’s corpuscles (found in the dermis) detect?
Sensitive to deep pressure and stretching
What do Pacinian corpuscles (found deep in the dermis) detect?
These are mechanoreceptors which are sensitive only to deep touch
- present in high numbers around joints for proprioception
Describe the pathophysiology of acne.
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
Name some possible clinical features of acne.
Papules Pustules Erythema Comedones (white/black heads) Nodules Cysts Scarring
What are some of the places acne can be found?
Face - easiest to treat
Chest
Back/shoulders
Occasionally found on the legs and scalp
Name some of the subtypes of acne.
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
How is acne vulgaris treated?
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
What are some of the side effects of acne treatment?
Topical agents may cause irritation, burning, peeling and can bleach clothes
Oral antibiotics can cause GI upset
OCP carries risk of DVT
What is the function of oral isotretinoin?
Oral retinoid for severe acne vulgaris
- contains concentrated vitamin A
16 week course at 1mg/kg
Acne remission in 80% of teenagers
What are the side effects of oral isotretinoin?
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
