What is the main purpose of tight junctions in epithelial cells?

The main purpose of tight junctions in epithelial cells is to prevent leakage of materials between adjacent cells. Tight junctions are specialized connections that form a barrier, sealing the spaces between cells so that substances passing through the epithelial layer must go through the cells themselves rather than between them. This is crucial in maintaining the integrity of epithelial layers, particularly in organs where selective absorption or secretion is essential, such as in the intestines and kidneys.

By regulating the movement of ions and molecules, tight junctions help maintain distinct environments on either side of the epithelium. This function is vital for processes such as nutrient absorption and barrier formation against pathogens. The tight sealing maintained by these junctions ensures that only specific substances can pass, thus allowing the epithelial tissue to perform its role effectively while preventing unwanted leakage.