Which type of junction between adjacent animal epithelial cells forms an impermeable seal that prevents leakage of extracellular fluid across the epithelial layer?
Answer and explanation
Correct answer: B. Tight junction
- Step 1: Epithelial sheets separate distinct physiological compartments (e.g., intestinal lumen from blood capillaries).
- Step 2: Tight junctions (zonula occludens) are formed by claudin and occludin transmembrane proteins that weld plasma membranes of adjacent cells together in a branching network.
- Step 3: This tight fusion obliterates the intercellular cleft, establishing a paracellular diffusion barrier that prevents leakage of luminal contents.
Answer
Tight junction (zonula occludens).
Why not the others: Adhering junction connects actin filament bundles of adjacent cells to coordinate mechanical movement; Gap junction contains connexon hemichannels allowing direct passage of ions and small signaling molecules; Desmosome anchors intermediate filaments to provide high tensile strength.
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