Which of the following statement(s) is/are correct concerning cell junctions?

a. The major occluding junction is the tight junction or zonula occludens

c. Desmosomes are button-like points of attachment which serve to weld together adjacent cells

d. Gap junctions are a type of cell junction specialized for cell communication

Cell junctions are classified as occluding, anchoring, and communicating. The major occluding junction is the tight junction or zonula occludens which connects cells in epithelia and thereby allows epithelia to serve as selective permeability barriers. Tight junctions are normally located near the apical pool of the cell and form a belt that completely encircles the cell. Anchoring junctions connect the cytoskeleton of the cell to the extracellular matrix or neighboring cells. Morphologically these are adherens junctions or desmosomes. Desmosomes are button-like points of attachment with a prominent intracellular plaque that serves to weld together adjacent cells by serving as anchoring sites for intermediate filaments within the cell. The third functional type of cell junction is a gap junction which is specialized for communication. This junction mediates both electrical and chemical coupling.