In a typical columnar epithelial cell, the junctional complex is arranged in a definite order from the apical to the basal surface. Which component occupies the most apical position?
- A Zonula adherens
- B Zonula occludens ✓
- C Macula densa
- D Desmosome
Correct answer: B. Zonula occludens
Explanation
The junctional complex runs from apex to base as tight junction (zonula occludens), then adherens junction (zonula adherens), then desmosome (macula adherens). The zonula occludens seals the intercellular space and maintains apicobasal polarity by preventing lateral diffusion of membrane proteins. Desmosomes and hemidesmosomes are spot-like attachments lying deeper, so they cannot be the most apical component. The classic mnemonic JAP: Junction, Adherens, Patch describes this apicobasal sequence.
Reference: Junqueira's Basic Histology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.