specialised tissues Flashcards
epithelial specialisation: recognise how epithelial function (including absorption, secretion, fluid transport and protection) is determined by the type and organisation of epithelial cells and summarise patterns of cell division found in different epithelia
what do epithelial cells require to function to ensure they are directional
polarity
what is key to having polarity
plasma membrane
what domains do junctions separate the epithelial membrane into
apical (open) and basolateral (matrix)
what allow directional flow and where are they located
polarised transporters restricted to specific parts of membrane
what do tight junctions do
seal paracellular pathway so any passage must be via cell, controlling passage
what is the fence function
maintains apical-basolateral polarity
epithelial specialisation: absorption - examples
nephron, small intestine, enterocytes
epithelial specialisation: absorption - requirements
absorptive, fluid transporting, selectively permeable, enterocytes possess striated brush border to increase SA
epithelial specialisation: absorption - direction of transport
apical membrane to basal lamina → capillary
epithelial specialisation: absorption - apical plasma membrane
many ion and water channels for passive transport
epithelial specialisation: absorption - basal lamina
mitochondria and membrane transporters for active transport (e.g. Na+/glucose coupling) at basal membrane infoldings (increase SA)
epithelial specialisation: secretion - examples
pancreas, goblet cells
epithelial specialisation: secretion - exocrine direction of transport
capillary → basal lamina to apical membrane
epithelial specialisation: secretion - exocrine
apical membrane leads to duct; secretory granules near apical membrane and RER and nucleus in basal cytoplasm
epithelial specialisation: secretion - endocrine direction of transport
apical membrane to basal lamina → capillary
epithelial specialisation: secretion - endocrine
secretory granules in basal cytoplasm; RER and nucleus near apical membrane; organised into glands (tubular and alveolar with varying complexities)