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)
4.
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.
7.
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.
10.
11.
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.
16.
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.
18.
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.