| Criteria | Tight Junction (Zonula Occludens) | Adherens Junction (Zonula Adherens) | Remarks |
| Primary Function | Acts as a barrier to prevent paracellular transport of solutes and water | Provides mechanical strength by linking actin cytoskeletons of adjacent cells | Tight junctions are for sealing; adherens junctions are for adhesion |
| Location | Apical-most part of the lateral membrane in epithelial and endothelial cells | Located just below tight junctions in epithelial tissues | Sequential organization: tight junction → adherens junction |
| Main Proteins | Claudins, occludin, junctional adhesion molecules (JAMs), ZO-1, ZO-2 | E-cadherin, β-catenin, α-catenin, p120 catenin | Distinct sets of transmembrane and cytoplasmic proteins |
| Cytoskeletal Association | Linked to actin filaments via ZO proteins | Strongly linked to actin filaments via catenin complex | Both connect to actin but through different adaptors |
| Permeability Regulation | Regulates selective permeability and maintains cell polarity | Does not regulate permeability but supports cell-cell adhesion | Tight junctions control permeability; adherens junctions do not |
| Role in Polarity | Essential for establishing and maintaining apico-basal polarity | Indirectly supports polarity by anchoring junctional complexes | Tight junctions are polarity gatekeepers |
| Dynamics and Plasticity | Dynamic and can be remodeled during inflammation, development, or cancer | Also dynamic; key in morphogenesis and epithelial-to-mesenchymal transition (EMT) | Both are responsive to signaling and cellular context |
| Tissue Distribution | Found predominantly in epithelial and endothelial monolayers | Ubiquitous in epithelial tissues and also present in other cell types | Tight junctions more restricted; adherens junctions are more broadly present |
| Pathological Relevance | Dysfunction leads to leaky barriers (e.g., IBD, cancer metastasis, viral entry) | Dysregulation affects cell adhesion and cancer progression (e.g., loss of E-cadherin) | Both are clinically significant in disease progression and infection |
