3: Epithelial Border Modifications & Glands Flashcards
Epithelial junctions
most part of the junctional complex located on the lateral border of epithelial cells
Tight junctions
outer membrane of neighboring cells is fused, sealing the intercellular space from the lumen
3 types of cytoskeletal linked junctions
- adherent junction
- desosomes
- hemidesmosomes
Adherent junction
forms an adhesion belt near apical surface beneath tight junction, membranes not totally fused but plasma proteins (anchored by actin filaments) interact with each other
Cadherins
the plasma proteins in adherent junctions
Terminal bar
tight junction and adherent junction
Desmosomes
similar to adherent junction but not located near the lateral luminal surface and have extracellular filaments which further anchor the membranes together
What cell types are desmosomes common in?
stratified squamous
Hemidesmosome
half a desmosome used to anchor the cell to the basal lamina
Gap juctions
proteins form a central pore between membranes to allow of electrical and chemical communication
What are microvilli composed of?
actin filaments
Microvilli purpose
increase surface area in absorptive epithelia
Striated border
microvilli in the gut
Brush border
microvilli in renal tubules
Stereocilia
branched microvilli found in the epididymis
What cell type are microvilli commonly found on?
simple columnar
What are cilia composed of?
microtubules