What is the macroscopic structure of skin?
- Colour
- Hair
- Thickness
- Laxity
- Oiliness
Who is vitiligo a bigger problem for?
Darker people
Which group is susceptible to acne?
Puberty
Which group is susceptible to UV induced sunburn?
Lighter skin
What is skin epidermis mainly made of?
Keratinocytes and their products
What are the four layers of skin epidermis, from top to bottom?
- Horny layer (stratum corneum)
- Granular layer (stratum granulosum)
- Prickle cell layer (stratum spinosum)
- Basal layer (Stratum basale)
What are the functions of the skin?
- Barrier
- Sensation
- Thermoregulation
- Pyschosexual communication
What are two types of dendritic epidermal cells?
Melanocytes and Langerhans cells
What are melanocytes?
- Dendritic cells of neural crest origin
- They occur at intervals along basal layer
- Require special stains to be seen
- produce melanin
What are Langerhans cells?
- Dendritic cells of bone marrow origin
- Found throughout prickle cell layer
- Immuno cells, highly specialised to present antigens to T-lymphocytes and mediate immune reactions
Which stain best shows the dermo-epidermal junction?
PAS stain
What is the significance of the dermo-epidermal junction in melanoma prognosis?
Retention of malignant melanoma above the junction is associated with good outlook
Where does keratinocyte differentiation mainly take place?
Basal layer
Which layer do daughter keratinocytes form by moving up?
Prickle cell layer, where keratinocytes lose ability to divide
What do keratinocytes produce?
Keratins, which contribute to epidermal strength
What happens in the granular layer?
Keratinocytes lose their plasma membranes and become corneocytes
What are keratohyalin granules?
- found in stratum corneum
- aggregations of keratin, phospholipase and cross link proteins (filaggrin aggregates keratins, involucrin is a major part of corneocyte envelope)
What is the horny layer made of?
Flatted corneocytes
What is the transit time of a keratinocyte from basal layer to horny layer?
30-40 days
What is the dermis made of?
Dense irregular connective tissue
What are the constituents of the dermis?
- Fibroblasts (secrete ecm; type 1 collagen and elastin)
- Blood vessels (smaller in superficial dermis, larger in deeper)
- Lymphatic vessels
- Mast cells (Distributed around blood vessels. When activated e.g. during allergic reactions, histamine is released causing increased vascular permeability and leakage of plasma into extravascular sites, causing local oedema. In the skin, this causes urticaria and ‘angio-oedema’.
- Nerves
Describe the condition of psoriasis
- affects around 2% of the population
- extreme proliferation of epidermal basal layer causing gross thickening of prickle cell layer and excessive stratum corneum production
What is malignant melanoma?
-Basal cell carcinoma, tumour of melanocytes
Describe the condition of vitiligo
- Autoimmune disease
- Immune system attacks melanocytes
