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.
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Extra cellular matrix is recently being explored in connection with cancer , metastases and autoimmune disorders. It is prepared for the benefit of both UG and PG medical and dental students.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Extra cellular matrix is recently being explored in connection with cancer , metastases and autoimmune disorders. It is prepared for the benefit of both UG and PG medical and dental students.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
1. Cell Junctions
Cell junctions are contact points between the plasma membranes of tissue cells.
The five most important types of cell junctions:
◦ Tight junctions,
◦ Adherens junctions,
◦ Desmosomes,
◦ Hemidesmosomes, and
◦ Gap junctions
2. Tight Junctions
Tight junctions consist of web like strands of transmembrane proteins that fuse the outer surfaces of adjacent plasma membranes together to seal off passageways between adjacent cells.
Cells of epithelial tissues that line the stomach, intestines, and urinary bladder have many tight junctions to retard the passage of substances between cells and prevent the contents of these organs from leaking into the blood or surrounding tissues.
3. Adherens Junctions
Adherens junctions contain plaque, a dense layer of proteins and to microfilaments of the cytoskeleton.
Transmembrane glycoproteins called cadherins join the cells.
Each cadherin proteins on the inside of the plasma membrane that attaches both to membrane in inserts into the plaque from the opposite side of the plasma membrane, partially crosses the intercellular space (the space between the cells), and connects to cadherins of an adjacent cell.
4. Adherens Junctions (contd.)
In epithelial cells, adherens junctions often form extensive zones called adhesion belts because they encircle the cell similar to the way a belt encircles your waist.
Adherens junctions help epithelial surfaces resist separation during various contractile activities, as when food moves through the intestines.
5. Desmosomes
Like adherens junctions, desmosomes contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intercellular space between adjacent cell membranes and attach cells to one another.
However, unlike adherens junctions, the plaque of desmosomes does not attach to microfilaments. Instead, a desmosome plaque attaches to elements of the cytoskeleton known as intermediate filaments that consist of the protein keratin.
The intermediate filaments extend from desmosomes on one side of the cell across the cytosol to desmosomes on the opposite side of the cell.
6. Desmosomes (contd.)
This structural arrangement contributes to the stability of the cells and tissue.
These spot-weld-like junctions are common among the cells that make up the epidermis (the outermost layer of the skin) and among cardiac muscle cells in the heart.
Desmosomes prevent epidermal cells from separating under tension and cardiac muscle cells from pulling apart during contraction.
7. Hemidesmosomes
Hemidesmosomes resemble desmosomes but they do not link adjacent cells. The name arises from the fact that they look like half of a desmosome.
However, the transmembrane glycoproteins in hemidesmosomes are integrins rather than cadherins.
On the inside of the plasma membrane, integrins attach to intermediate filaments made of the protein keratin.
Tissues, Organs and Systems: The images have big font size and reduced background color. Useful for smartphones, classroom and printouts. The rest is standard stuff.
This presentation was a hard work of investigation and searching time by veterinary students of ULPGC Gran Canaria university. we learned to much about cytology in the process of recompilation of information. We share this knowledge with the desire that it may be useful and instructive for some one interested in cience or maybe other student arround the world. enjoy it!
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.
