Rest of it Flashcards
Two different domains of the membrane?
Apical domain (at lumenal,open, surface) and basolateral domain in contact with the MBC.
Why is polarity needed?
- To give directionality needed for highly specific epithelial function
- Example: Na+ K+ pump, no net direction if unpolarised membranes
Tight junction?
Belt at apical lateral domain to seal gap between cells
Adherens junction?
Controls formation of other junctions, ‘master’ junction
Desmosomes?
Mechanically tough junctions, resist mechanical stresses
Gap junction?
Form pores between cells and allow material exchange between cells
Two facts about transporting epithelia?
- High concentration of ion transporters at apical plasma membrane
- High concentration of mitochondria at basal membrane for active transport
Where are carriers transporting nutrients usually found in absorptive epithelium?
Microvillous brush-border membranes, which have large surface areas
Exocrine vs endocrine?
Into a duct or lumen vs into the bloodstream
Constitutive cells?
Secretory vesicles, as they are formed, move directly to the plasma membrane and release their contents (exocytosis)
Stimulated cells?
Secretory vesicles are stored in the cytoplasm and only fuse with the cell membrane to release their contents, e.g release of adrenaline from cells of the adrenal medulla
Why and how are epithelial cells replaced?
Many cells are lost by cell death or abrasion and are replaced by the proliferation of stem cells within the epithelium
Stem cells in villus epithelium?
Crypt stem cells
Chemotherapy effects?
Many chemotherapy agents have gastro-intestinal side effects due to the inhibition of the proliferation of intestinal crypt cells
Hyperproliferation?
Increased cell numbers and thickening of cell layers in response of repeated or constant pressure. Cells can form a hard layer called ‘hard skin’ or ‘corns’
