ABSTRACT
Cells may cling to one another through direct cell–cell junctions, or they may be bound together by extracellular materials that they secrete; but by one means or another, they must cohere if they are to form an organized multicellular structure. Thus, the apparatus of cell junctions, cell adhesion mechanisms, and extracellular matrix is critical for every aspect of the organization, function, and dynamics of multicellular structures. The structures of cell-cell adhesions are most clearly seen in mature epithelia and in some other tissues, such as heart muscle, that are held together by strong direct anchorage of cell to cell. The cadherin superfamily is central to cell-cell adhesion in animals, but at least three other superfamilies of cell-cell adhesion proteins are also important: the integrins, the selectins, and the adhesive immunoglobulin-superfamily members. A summary of the various cell junctions found in a vertebrate epithelial cell, classified according to their primary functions.
