Skin pathology (9.1) Flashcards
Outline the structure of normal skin
Epidermis: Keratinised stratified squamous epithelium (keratinocytes)
- Stratum basale
- Stratum spinosum
- Stratum granulosa
- Stratum lucidem
- Stratum corneum: No nucleus
Dermis: Dense, irregular connective tissue. Papillary and reticular dermis
Hypodermis: Adipose tissue and main blood supply
NOTE:
Desmosomes = Between cells
Hemidesmosomes: Between the epidermis and the dermis
Outline the function of skin
- Barrier: Keratin → microorganisms. Phospholipid → waterproof
- Protection from external damage: UV light, chemical, thermal and resistance to sheer stress
- Sensation
- Metabolic: Synthesis of Vitamin D3. Subcutaneous fat = major energy source
Skin intact ⇒ very diffficult for bacteria to gain entry
- Adhesion
- Organisation of cells (controlling growth and differentiation - downwards)
Name the cell types associated with skin and their functions
Keratinocytes: 95 % of cells
- Stratified squamous keratinising epithelial cells
- Produce keratin
Melanocytes:
- Pigment synthesising (hair and skin)
- Neural crest derived
- In the stratum basale
- Melanosomes in the cytoplasm contain melanin and are passed to keratinocytes → scattering of UV light
Langerhan’s cells:
- In all layers but prominent in the stratum spinosum
- Bone marrow derived
- Dendritic, antigen presenting cell
Merkle cells:
- A clear cell in the stratum basalis
- Neuroendocrine function
- Connected to keratinocytes and afferent nerves
Outline the features of the epidermal-dermal junction
Basement membrane: At the interface between the parenchyma and support tissues
- Type IV collagen, glyocproteins and GAGs
Hemidesmosomes
Outline the blistering diseases of the skin
A group of diseases caused by autoantibodies against the epidermis or basement membrane
-
Pemphigus:
- IgG auto-antibodies against desmosomes: acantholysis seen
-
Bullous pemphigoid:
- Deposition of IgG auto-antibodies to BM proteins
-
Dermatitis herpetiformis:
- Deposition of IgA auto-antibodies to fibrils that bind the BM to the dermis
- Associated with coeliac disease
-
Epidermolysis bullosa:
- Causes separation of the epidermis from the dermis with minimal shearing foces - no inflammatory cell infiltrate
- Subtypes:
EB simplex: Defecti8ve cytoskeleton
Junctional EB: Defective hemidesmosomes
Dystrophic EB: Defective BM collagen
Describe the common inflammatory conditions of the skin (dermatitis)
Eczema, psoriasis, infection
Outline the infectious diseases of the skin
Define the terminology associated with skin lesions
Acantholysis; spongiosis; acanthosis; hyperkeratosis; paraketatosis; actinic keratosis
Acantholysis: Loss/lysis of desmosomes
Spongiosis: Collection of fluid within the epidermis
Acanthosis: Thickening of the skin (stratum spinosum in eczema)
Hyperkeratosis: Thickening of keratin
Paraketatosis: Retention of nuclei within the cells of the stratum corneum
Actinic keratosis: Thickening of the skin associated with sun exposure
Describe the pathological features of skin cancers
Define epidermolysis bullosa
A blistering skin condition associated with separation of the dermis from the epidermis, with minimal shearing forces. No inflammatory cell infiltrate present.
Different types are seen - dependent upon where the break happens,
