Epithelium Flashcards
What are terminal bars?
Terminal bars are junctional complex at the LM level. Once TEM came out they could look and see the junctional complexes
junctional complex
Tight Junction (zona occludens) then Adhering junction (zona adherens) then Desmosomes (macula adherens)
“zonula” = band or belt
“macula” = spot
paracellular v. transcellular pathway
Paracellular: between adjacent epithelial cells (passive diffusion)
Transcellular pathway: through the epithelial cell (active transport)
occludin v. claudin
occludin (most ZOs) v. claudin = aqueous pores.
The more claudin there is, the less “tight” the tight junction will be.
where are CAMs (E-cadherin) found and what do they link to in the inside of cells?
CAMs are found at adherens junctions (zona adherons) and they are linked to ACTIN filaments
basement membrane
it the light microscopic term for the layer of ECM that lies between the basal domain of the epithelial cell and the CT. BMs stain specifically with PAS (ie made of carbohydrates [glycolipids/glycoproteins])
integrins
transmembrane proteins in both junction at the basolateral membrane.
focal adhesions
@ the basolateral side of epithelial cells
Actin (cytoskeleton) linked by Intergrins to BL components.
very dynamic, make/break, mechanosensitivity
hemidesmosomes
@ the basolateral side of epithelial cells
intermediate filaments via attachment plaque linked by integrins to BL components
strong stable adhesion (resists abrasion)
what are the BL components and what are they synthesized by?
BL components are synthesized and secreted by epithelial cells:
Lamina, Type IV collagen, Fibronectin, Proteoglycans
Reticular lamina, its components, and where these components are made/secreted by?
RL is the e- lucent area beneath the BL. RL components are synthesized and secreted by fibroblasts (CT cells)
fibronectin & laminin
Collagen fibers
anchoring fibers and plaques
thickness of RL varies with frictional force applied to overlying epithelium.
disorders of adhering-type junctions (especially the strong ones) would produce what problem?
blisters
