Final answer:
Epithelial cells are tied together by cell junctions, notably tight junctions that prevent leakage between cells, and anchoring junctions like desmosomes that provide stability.
Step-by-step explanation:
Epithelial cells are held together along their lateral, superficial surfaces by extracellular barriers called cell junctions. There are three major types of these junctions: tight junctions, anchoring junctions, and gap junctions. Tight junctions, also known as zonula occludens, are particularly important in creating an impermeable barrier that prevents materials from passing between cells. Anchoring junctions include types like desmosomes, hemidesmosomes, and adherens, which provide mechanical stability and are critical in tissues that undergo stress, such as skin and heart muscles. Lastly, gap junctions allow for communication between cells by permitting the passage of small molecules and ions.