Biology · Ch 10 — Animal Tissue
Cell Junctions
Cell Junctions
Epithelial cells do not simply sit next to one another — they are physically connected to their neighbours, and to the basement membrane beneath them, by a set of specialised junctional structures called cell junctions. Five distinct kinds of cell junction are recognised, each with its own role in holding the sheet together and letting its cells communicate:
- Tight Junctions (TJs) maintain the polarity (the distinct 'top' and 'bottom' character) of the cell and stop proteins and ions from diffusing sideways between adjoining cell membranes, sealing the sheet against leakage.
- Adherens Junctions (AJs) take part in various cell-signalling pathways and in regulating gene transcription within the joined cells.
- Gap Junctions (GJs) are direct channels between the cytoplasm of neighbouring cells that let ions and small molecules pass straight through, allowing cells to exchange chemical signals with one another. …
Tight Junctions (TJs): maintain cell polarity and prevent lateral diffusion of proteins and ions between adjoining cell membranes.
Adherens Junctions (AJs): involved in various cell-signalling pathways and transcriptional regulation.
Gap Junctions (GJs): intercellular channels that allow passage of ions and small molecules, and exchange of chemical messages, directly between adjacent cells.
Desmosomes (Ds): provide mechanical strength to epithelial tissue, cardiac muscle and the meninges. …