In many plant tissues, it turns out that the plasma membrane of each cell is continuous with that of the adjacent cells. The membranes contact each other through openings in the cell wall called Plasmodesmata . The portion of the cell exposed to the lumen is called its apical surface.
Tight junctions seal adjacent epithelial cells in a narrow band just beneath their apical surface.
This pathway provides control over what substances are allowed through. Thus the special functions of each surface, for example receptor-mediated endocytosis at the apical surface exocytosis at the basolateral surface can be preserved. Adherens Junctions Adherens junctions provide strong mechanical attachments between adjacent cells. They hold cardiac muscle cells tightly together as the heart expands and contracts. They hold epithelial cells together.