Dermatology Flashcards
What are the 6 functions of the skin
- Chemical, Thermal, Physical, UV protection from environment
- Thermoregulation
- Neuroreception
- Antigen Processing
- Vitamin D Synthesis
- Cosmetic
Describe the Epidermis.
The layers present.
Cells found in them
How does epidermis change in different parts
Epidermis
- Keratinocytes:
o from top to bottom: basal stratum granulosum (cells connected by desmosomes) stratum corneum-provides a relatively impermeable barrier to inward penetration by chemicals, micro-organisms and allergens, combined with melanin it also provides protection against ageing and carcinogenic effects of UV radiation
o Basal layer cells are undifferentiated stem cells which differentiate as move up towards surface
- Langerhans cells
o antigen presenting cells.
- Epidermis thickness varies around body, i.e. soles of feet (sites of trauma/friction) thicker than around flexion areas (inside elbow)
What is the Basement Membrane Zone
What layers make it up
Basement membrane zone (BMZ):
Junction between epidermis and dermis below
Important structural role. Also acts as a barrier to inflammatory and neoplastic cells. The BMZ includes the following components:
• basal keratinocyte (hemidesmosomes)
• lamina lucida
• lamina densa
• sub-lamina densa (papillary dermis)
Describe the function of the Dermis.
What is contained within it and what functions do they serve
Nourishes the epidermis and interacts with it during embryogenesis, wound repair and remodelling
Connective Tissue collagen, elastin and ground substance provide strength, elasticity to protect against shearing forces
BVs and Eccrine glands vital in thermoregulation.
Apocrine Glands secrete viscous liquid with distinctive body odour
Nerves makes the skin an important neuroreceptor sense organ interacting with the environment
Hairs follicles- cosmetic and thermoregulative role of hair
Fat Layer- protection and thermoregulation
Macule
circumscribed
flat
change in colour
less than 1cm diameter
Papule + Nodule
circumscribed palpable elevations
less than 1cm –> papule
greater than 1cm –> nodule
Patch
Flat lesion less than 1cm diameter
Plaque
Flat slightly elevated
Scaly
Greater than 1cm diameter
Pink and distinct edge
Vesicle + Bulla
Raised fluid filled lesions
Less than 0.5cm in diameter is vesicle
Greater than 0.5 is bulla
Wheal and Telangiectasia
Wheals are transient pink/red swellings with central pallor
T’tasia refers to dilatation of capillaries
Secondary Infections:
Crust
Excoriation
Lichenification
Scar
Erosion
Ulcer
Atrophy
Crust- dried exudate
Excoriation- scratching causing shallow haemorrhagic excavation into skin which can lead to introduction of bacteria (impetiginisation)
Lichenification- scratching causing skin to become thickened and leathery and creased. common in flexion sites
Both excoriation and lichenification commonly occur in severe atopic eczema pts.
Scar- final stage of healing involving dermis resulting in smooth shiny lesion with loss of appendages/adnexae
Erosion- partial break in epidermis which heals without scarring unless secondary infection occurs
Ulcer- full thickness loss of epidermis which heals with scarring
Atrophy- thinning and translucency of skin with loss of skin markings
Eczema What is it? What are the characteristic patterns of skin involvement? Compare acute v chronic presentation List the 5 main subtypes
Eczema is puritic inflammation associated with dryness and erythema of the skin.
Eczema is caused by atopic dermatitis. This is a genetic predisposition to having an IgE hypersensitivity reaction. Often presents in childhood alongside other atopic conditions such as asthma, hay fever.
Has characteristic patterns of skin involvement
Babies –> extensor surfaces, face
Child –> flexures
Adult –> generalised, discoid
Eczema can be Acute or Chronic
Acute –> redness, weeping, papules, vesiculation
chronic –> dryness, scaling, lichenified
Flexural Seborrheic Varicose Discoid Lichen simplex chronicus
What can happen as a result of Scratching of Eczema lesions?
Scratching of lesions often leads to excoriation and lichenification and introduction of bacteria can lead to secondary lesions whose appearance will be dependent on the introduced bacteria. S. aureus sec’ infection known as ‘impetiginisation’ gives yellow crust and weeping.
Herpes simplex gives monomorphic vesicles known as ‘eczema herpeticum’
What are the 3 main forms of non-atopic dermatitis?
Why are they known as ‘exogenous eczema’
Contact dermatitis- includes contact allergic (often associated with occupation/hobbies and site of lesions provides clues) and irritant contact (frequent hand washing or exposure to irritants). Can be identified by patch tests
Drug-induced dermatitis occurs rarely. Severe drug hypersensitivity reactions in days/weeks after initial drug exposure.
Known as exogenous eczema as present just like atopic eczema
Outline treatment of Eczema and non-atopic dermatitis forms
Treatment (for atopic + non-atopic)
- Avoidance of known allergens e.g. pets, house dust,
- Regular emollients (skin-softeners, moisturisers, soaps. Eczema is dry: general rule in dermatology is if its dry, wet it; if its wet, dry it)
- Topical steroids to treat itching
- Antibiotics if skin impetiginized
- Antihistamine for a sedative affect, to help patients sleep at night
- Wet wraps, helps soothe and introduce moisture into the skin and especially in children, protects them from itching and secondary infections
- Occasionally systemic immunomodulating therapy e.g. prednisolone, azathioprine, cyclosporin
- UVB, PUVA (phototherapy)
