L8 - Epithelia Flashcards
what does it mean if an epithelial cell has a large nucleus?
it may produce a lot of protein
what are epithelial tissues main functions? 2
protective barrier and absorption and secretion
what cellular junctions are occluding? where are they found?
tight junctions (zonula occludens), found apically at the cell
what cellular junctions are anchoring? 3
zonula adherens, desmosomes, hemidesmosomes
what do zonula adherens do?
link cells together by the actin cytoskeleton
what do desmosomes do?
anchor cells together
what do hemidesmosomes do?
anchor cells to the basement membrane
what cellular junctions are for communicating? how so?
gap junctions, allow for small molecules to travel in between the gaps
what are zonula occludens (tight junctions) transmembrane proteins?
occludin and claudin
what do different claudins cause?
different permeabilities in different tissues
what effect does claudin-16 have on the kidney?
makes only specific regions are permeable to Mg2+ ions
what effect does a mutation inclaudin-16 gene have on the kidney?
causes abnormal claudin-16 resulting in junction impermeable to ions and so low Mg2+ reabsorption back into the blood
what conditions can be caused by mutated or faulty claudins? 3
magnesium deficiency, kidney damage/renal failure, dehydration via skin
what is claudin-1 responsible for?
waterproofing qualities of the skin
what is zonula adherens (adherens junction) main transmembrane protein?
E-cadherins
what disease is linked to the loss of E-cadherins?
metastasis of cancer cells
what kind of cancerous cells have lower levels of E-cadherin expression?
malignant
desmosomes also called?
macula adherens
how do desmosomes anchor cells together?
link cytoskeletons of adjacent cells by connecting cytokeratin (intermediate filaments)
what is a desmosomes main transmembrane protein? example?
cadherins e.g. desmoglein
what is pemphigus vulgaris?
an autoimmune disease
what do antibodies attack if you have pemphigus vulgaris disease?
desmoglein 3
what happens to your skin cells when you have pemphigus vulgaris?
cells fall apart, skin sloughs off
cadherins are important for…
maintaining structural integrity of epithelium
where are hemidesmosomes found in the cell?
basal surface of cell
what do hemidesmosomes bind to?
cytokeratin
what are hemidesmosomes main transmembrane proteins?
integrins
what are gap junctions main transmembrane proteins?
connexins
what is a connexon?
when a connexin forms a channel that can open/close to allow passage of ions and small molecules
epithelial tissue is polarised and linked as sheets through…
lateral junctions
specialisations are linked to ___ of the cell?
polarity
what does microvilli provide?
increased surface area
what makes up the core of microvilli?
parallel actin bundles
what are non-motile cilia function?
sensory information, protection
what are motile cilia function?
beat in rhythm to move substances across surface of epithelium
example of motile cilia
respiratory tract
what is cilia’s cytoskeleton composed of?
a core of microtubules
what is the basement membranes structural role?
binds epithelial cells to connective tissue
both epithelia and connective tissue excrete molecules that come together to form what?
basement membrane
what is the basement membrane’s structure?
sheet-like arrangement of ECM proteins
why does epithelia allow nutrients to pass through?
because epithelia isn’t vascularised
what does the basement membrane do? 2
regulates permeability, controls growth and direction
what three layers of basement membrane can be seen under electron microscopy? how are these layers distinguished?
lamina lucida - quite clear, lucid
lamina densa (aka basal lamina) - denser, easer to see
lamina fibroreticularis
what does basal folding do?
increases surface area on basal surface of cell
