What are the three main functions of the skin?
- Protection
- Regulation
- Sensation
Explain the protective skin function
- Primary function as a barrier
- Mechanical impacts
- Protects and detects pressure
- Detects variation in extreme temperature
- Barrier to micro-organisms
- Barrier to radiation/chemicals
Explain the regulatory function of the skin
- Body temperature regulation via sweat, hair and changes in peripheral circulation
- Fluid balance via sweat/sensible loss
- Synthesis of vitamin D
Explain the sensation function of the skin
• Network of nerve cells that detect and relay changes in the environment
- heat
- cold
- touch
- pain
What are the 4 main layers of the skin?
- Epidermis
- Basement membrane
- Dermis
- Sub cutaneous tissue
What are the layers of the epidermis?
- Stratum corneum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
What does the histology of the stratum spinosum look like?
There are processes (spines) between the cells
What embryological structure is the skin derived from?
The ectoderm
Explain the embryology of the skin
- Derived from ectoderm
- 5th week: skin of 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 periderm
- The epidermis invaded by melanoblasts, cells of the neural crest origin
In embryology, what forms the sebaceous glands and sweat glands?
- The cells of the epithelial root sheath proliferate to form a sebaceous gland bud
- Sweat glands develop as downgrowths of epithelial cords into the dermis
What are Langerhans and where are they located?
- Members of the dendritic cell family
* In the basal layers
Explain the immune response/system in the skin
•Specialize in antigen presentation:
- acquire in antigens in peripheral tissues
- transport them to regional lymph nodes
- present to naive T cells and initiate the adaptive immune response
•Activated T cells initiate cytokine release cascade
What are the effects of UV on the skin?
- Direct cellular damage
- Alterations in immunological function
- Photoaging
- DNA damage
- Carcinogenesis
What tumour suppressor gene mutated by DNA damage is associated to melanoma?
P53
Which cells protect form UV DNA damage?
- Keratinocytes
* Melanocytes
What absorbs UVB in the skin?
7-dehydrocholesterol
What does 7-dehydrocholesterol in the skin convert UVB to?
Previtamin D3
What is pre-vitamin D3 converted to?
Active vitamin D3 (converted in the plasma membrane)
What are the associations of a vitamin D deficiency?
- Increased risk of common cancers
- Autoimmune diseases
- Infectious diseases
- Cardiovascular disease
What cells are associated with free nerve endings?
Merkel cells
Explain what Merkel cells are
- At the base of the epidermis
- Respond to sustained gentle and localised pressure
- Assess shape/edge
Explain what meissner corpuscles are
- situated immediately below epidermis
- Particularly well represented on the palmar surfaces of the fingers and lips
- Especially sensitive to light touch
Explain what Ruffini corpuscles are
- Situated in the dermis
* Sensitive to deep pressure and stretching
Explain what pacinian corpuscles are
- Mechanoreceptors present in the deep dermis
- Sensitive to deep touch
- Rapid deformation of the skin surface
- Around joints for position/proprioception
