Question:
Which of the following intercellular junctions seals the paracellular space and is classified as a tight (occluding) junction?
Which of the following intercellular junctions seals the paracellular space and is classified as a tight (occluding) junction?
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Which junction uses claudins/occludins to seal the apical paracellular space?
Updated On: Jun 25, 2026
- Fascia adherens
- Desmosome (macula adherens)
- Gap junction
- Zonula occludens
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The Correct Option is D
Solution and Explanation
Step 1: Classify cell junctions. Intercellular junctions fall into three functional groups - occluding (tight) junctions that seal, anchoring/adhering junctions that bind cells/cytoskeleton, and communicating (gap) junctions that exchange ions.
Step 2: Identify the occluding junction. The zonula occludens (tight junction) is the apical-most band that fuses adjacent plasma membranes via claudins and occludins, obliterating the paracellular space and creating the diffusion barrier/cell polarity. It is the occluding junction asked for.
Step 3: Eliminate the adhering and communicating junctions. Fascia adherens is a broad adherens-type junction of intercalated discs anchoring actin in cardiac muscle. Desmosome (macula adherens) is a spot junction anchoring intermediate filaments (cadherins to plakins) - pure mechanical adhesion. Gap junction is a communicating junction (connexons) for ionic/metabolic coupling, not sealing.
Step 4: Conclude. Only the zonula occludens is the tight occluding junction that seals the intercellular cleft.
Key fact: Zonula occludens = tight junction, formed by claudins/occludins, sealing the paracellular pathway.
Step 2: Identify the occluding junction. The zonula occludens (tight junction) is the apical-most band that fuses adjacent plasma membranes via claudins and occludins, obliterating the paracellular space and creating the diffusion barrier/cell polarity. It is the occluding junction asked for.
Step 3: Eliminate the adhering and communicating junctions. Fascia adherens is a broad adherens-type junction of intercalated discs anchoring actin in cardiac muscle. Desmosome (macula adherens) is a spot junction anchoring intermediate filaments (cadherins to plakins) - pure mechanical adhesion. Gap junction is a communicating junction (connexons) for ionic/metabolic coupling, not sealing.
Step 4: Conclude. Only the zonula occludens is the tight occluding junction that seals the intercellular cleft.
Key fact: Zonula occludens = tight junction, formed by claudins/occludins, sealing the paracellular pathway.
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