Name the main epithelial cell junctions and their primary functions.

• A. Tight junctions seal apical surfaces; adherens junctions link to actin; desmosomes provide mechanical strength via intermediate filaments; gap junctions allow passage of ions and small molecules between cells.
• B. Tight junctions allow passage of ions; gap junctions seal surfaces; adherens junctions anchor cells to the basement membrane; desmosomes transport metabolites.
• C. Tight junctions seal apical surfaces; gap junctions anchor cells to the basement membrane; adherens junctions prevent leakage; desmosomes exchange ions.
• D. Desmosomes seal apical surfaces; hemidesmosomes link cells to the basement membrane; gap junctions attach cells to extracellular matrix.

Answer: (A)

In epithelial tissues, four main intercellular junctions work together to create a functional barrier and keep the tissue cohesive. Tight junctions form a seal at the apical surface that prevents paracellular leakage and helps establish cell polarity. Adherens junctions attach to the actin cytoskeleton through cadherin-catenin complexes, creating belt-like connections that help cells maintain shape and transmit mechanical forces during tissue remodeling. Desmosomes grip the cells with strong adhesion by linking to intermediate filaments, providing substantial mechanical strength to resist stretching and shear. Gap junctions form channels between neighboring cells, allowing ions and small metabolites to diffuse directly from one cell to another, enabling electrical and metabolic coupling. The combination of these functions explains how epithelia stay a selective barrier while remaining mechanically resilient and communicative. The other descriptions mix up which junction does what or whether they connect to the basement membrane, which is characteristic of cell-matrix junctions rather than cell–cell junctions.