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tight junctions formed by the fusion of integral proteins of the lateral cell membranes of adjacent epithelial cells, limiting transepithelial permeability.
Etymology: ME, thight, strong; L, jungere, to join
the zonula occludens of the junctional complex between cells in which the plasma membranes of adjacent cells are in direct contact and where there is no intercellular space.
tight junc·tion(tīt jŭngk'shŭn)
An intercellular junction between epithelial cells in which the outer leaflets of lateral cell membranes fuse to form a variable number of parallel interweaving strands that greatly reduce transepithelial permeability to macromolecules, solutes, and water through the paracellular route.
Refers to cells in which their membranes are fused rather than separated by a small extracellular space. The movement of substances through that space is restricted. Syn. zonulae occludentes. See blood-brain barrier.
a cell junction in which there is no intercellular space between cell membranes and so is impermeable. See also cell junction.