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Cell junctions

Cell junctions. INTERCELLULAR JUNCTION. 1. Tight junction 2. Gap junction 3. Desmosomes. 1.Tight junctions Ridge like structures between adjacent cells. Made up of proteins Cells are bound together . Found in epithelial cells intestinal mucosa renal tubles

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Cell junctions

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  1. Cell junctions

  2. INTERCELLULAR JUNCTION 1. Tight junction 2. Gap junction 3. Desmosomes

  3. 1.Tight junctions • Ridge like structures between adjacent cells. • Made up of proteins • Cells are bound together . • Found in epithelial cells • intestinal mucosa • renal tubles • Form selective barrier Eg.Blood brain barrier .

  4. Functions Helps in maintaining the functional polarity. Localizing the membrane proteins in one place.

  5. They are important in preventing molecules leaking between the cells and providing control of passage for materials through the epithelial sheet. • It is made up of proteins called claudins and occludins.

  6. 2.Gap junctions or communicating junctions . Gap junctions form channels between cells. Allow ions and small molecules to pass directly from one cell to another. These channels are formed by membrane proteins called connexin. Six connexins in the cell membran form a channel called a connexon

  7. Functions • Gap junctions permit electrical signals to pass directly from one cell to another. • Gap junctions are found in heart and smooth muscle cells and between some neurons. • To regulate the membrane potential between cells and allow electrical impulses to pass between cells. • Electrical impulses passing between cardiac muscle cells it lead conduction of the beat. • Also gap junctions provide the contractions of the smooth muscle cells of the uterus during birth

  8. Microvilli Plasma membranes of adjacent cells Intercellular space Basement membrane Intercellular space Channel between cells (connexon) Figure 3.5c

  9. 3. Desmosome or maculae adherens • fasten cells together strengthening the tissue. • Desmo (‘bound’), soma (‘body’). • Adjacent membranes become thickened and the space in between is filled with filament like material. • Fibrils arise from this portion to the interior of the membrane. • Hemi desmosome – half desomoses on the basal sides of the cell .

  10. Microvilli Plasma membranes of adjacent cells Intercellular space Basement membrane Intercellular space Plaque Intermediate filament (keratin) Linker glycoproteins (cadherins) (b) Desmosomes: Anchoring junctions bind adjacent cells together and help form an internal tension-reducing network of fibers. Figure 3.5b

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