Integument 3 Flashcards
hoofs, footpads and antlers
What type of epithelium would be found in the footpads?
- keratinised stratified squamous epithelium because they are thick
What is the epidermis?
- a self-renewing stratified squamous keratinising epithelium
How can the epidermis do constant turnover of skin cells?
- the moving escalator
How can the moving escalator provide protection?
- accelerated turnover can be protective e.g., noxious stimuli on skin surface
- thickening also protects if trauma (e.g., if an animal scratches a lot thickening can prevent breaking skin)
How can cross-linkage of keratin filaments occur in cornification?
- by enzyme like profilagrin in keratohylaine granules and envelop proteins
What are envelop proteins important for in cornification?
- waterproofing
In cornification and keratinisation there is also a lipid seal between corneocytes what is this called and what does it lead to?
- bricks and mortar
- this means that if things want to cross the skin then they will have to cross intracellularly, transcellularly or transfolicaularly
What do Hemi-desmosomes do?
- anchor basal cells to basement membrane
What do desmosomes do?
- attach keratinocytes to each other in a deeper layer of the dermis
What do corneo-desmosomes do?
- attach corneocytes to each other (enzymatically degrade -> desquamation)
What can be targets in autoimmune disease?
- the proteins comprising desmosomes and hemi-desmosome
A major function of the epidermis to act as a what?
- a barrier
What does the epidermal barrier do?
- keep water, electrolytes and macromolecules in
- keep infectious agents and chemicals out
How does the epidermal barrier contribute to homeostasis?
- water and electrolyte balance
- temperature and thermoregulation
The epidermal barrier also provides protection via the epidermal layers themselves plus specialised epidermal structures - what are these?
- Hair (physical protection, UV, sensory, swatting)
- Antioxidant (vitamin E in) sebaceous gland secretion
- Hooves, claws and nails as weapon and barriers
The stratum corneum is the bricks and mortar - what are corneocytes (the bricks)?
- flattened cells
- aggregation of keratin filament (by filaggrin)
- cell membrane is converted to a resilient cell envelop consisting of cross-linked protein covalently bound lipids
The lipids in the stratum corneum make the bricks what happens here in terms of water proofing?
- lipids released from stratum granulosum into intracellular space
- included ceramides, cholesterol, long chain fatty acids
- hydrophobic, so prevent transepidermal water loss
- the keratinocyte and sebum-derived lipids also make the epidermis waterproof
There are huge number of factors influencing the skin but limited ways for the skin to respond - what are these responses?
- alterations in epidermal growth or differentiation
- alterations in epidermal fluid balance and cellular adhesion
- inflammation of epidermis
- alterations in epidermal pigmentation
What two things can result from alteration in epidermal growth or differentiation?
- abnormal cornification
- epidermal hyperplasia
What is abnormal cornification?
- insult affects balance between proliferative basal cells and loss of corneocytes
What can cause abnormal cornification?
- inflammation, surface trauma, metabolic or nutritional disorders, the environment
What can abnormal cornification result in?
- can result in hyperkeratosis (thickened stratum corneum)
Alteration is epidermal growth or differentiation can also lead to epidermal hyperplasia what is this?
- alteration of epidermal growth and proliferation (increased number of cells, usually in stratum spinosum)
What is epidermal hyperplasia often a very common response to?
- A variety of stimuli, often chronic like allergies