What is a primary characteristic of tight junctions?

Tight junctions play a crucial role in maintaining the integrity of epithelial layers by forming a selective barrier between adjacent cells. They are composed of a network of proteins that connect the membranes of neighboring cells together, creating a seal that prevents the passage of materials through the intercellular space. This characteristic is essential for maintaining a distinct environment on either side of the tissue and regulating the movement of ions, small molecules, and water selectively. This barrier function is vital in various tissues, including those in the intestines, blood-brain barrier, and renal tubules, where it helps to protect underlying tissues and ensure proper physiological functions.

While cell communication, growth encouragement, and nerve signal transmission are important aspects of cellular interactions, they do not specifically define the role of tight junctions in the context of maintaining selective permeability and structural integrity between cells.