Intercellular junctions are specialized structures that allow adhesion and communication between cells in multicellular organisms. There are three main types: gap junctions, tight junctions, and anchoring junctions. Gap junctions consist of channels that connect adjacent cells and allow for signal transfer. Tight junctions form a continuous belt around cells and prevent fluid leakage between epithelial layers. Anchoring junctions include desmosomes, hemidesmosomes, and adherens junctions, which anchor cells to each other and extracellular fluid through various transmembrane proteins and cytoskeletal elements.
2. Intercellular junctions
• A cell junction is a type of structure that exists
within the tissue of some multicellular organisms.
• specializations of the cellular margins that
contribute to the adhesion or allow for
communication between cells.
• Mostly found in epithelial tissues.
3. CONT…
There are three main types:
• Gap junction (nexus).
• Tight junction (zonula occludens)
• Anchoring junction
-Desmosome (macula adherens)
-Hemidesmosome
-Adheren (zonula adherens)
5. Gap Junction:
• It is a communicating junction.
• Gap junctions consist of intercellular channels in
the plasma membrane of adjacent cells.
• Consist of six connexon proteins arranged to form
a doughnut shape structure.
• Play role in cardiac muscle contraction.
6. Cont…
• Helps in signal transfer in brain.
• Their size vary in different cells.
8. Tight Junction:
• The borders of two cells are fused together, often around the
whole perimeter of each cell, forming a continuous belt like
junction known as a tight junction or zonula occludens (zonula =
latin for belt).
• ZO-1 & ZO-2 Link transmembrane proteins (Occludin and
Clauding) with Spectrin.
• Prevent leakage of fluid.
• Found in the apical region around the cell's circumference.
9. Cont…
• It prevent mobility of transmembrane proteins.
• It regulate the movement of water and solutes
between epithelial layer.
• Lines the gastrointestinal tract.
12. Anchoring Junction:
• Cells within tissues anchor to one another and
to extracellular fluid.
• There are following three types:
1. Desmosomes Junction
2. Hemidesmosomes Junction
3. Adherens Juntion
14. Desmosomes:
• Form cell to cell junction.
• Known as Maculae adherens.
• Intracellular adaptor proteins connect to
intermediate filament and form cytoplasmic
plaque.
• Cadherin joins the cytoplasmic plaques of two
cells.
15. Cont…
• The gap b/w this junction is 30nm
• Found in epidermis of skin and muscle tissues.
• Blistering diseases.
• Pemphigus.
• Hailey-Hailey disease.
17. Hemidesmosomes:
• Connect cell to extracellular fluid.
• Connect epithelial cells to basement
membrane.
• Integrins are the linking proteins.
• Present in epidermis of skin.
• Epidermolysis bullosa.
19. Adheren Junction:
• Junctions which form junction b/w cell to cell.
• Also known as Zonulae adherens.
• Lies basal to tight junction.
• Microfilaments of two cells are connected by cadherins.
• Cytoplasmic face is linked to actin cytoskeleton.
• Actin myosin interaction can change the shape of the
epithelium.