Cell Junctions - completely encircles each cell, preventing...

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Cell Junctions The plasma membranes of adjacent cells are usually separated by extracellular fluids  that allow transport of nutrients and wastes to and from the bloodstream. In certain  tissues, however, the membranes of adjacent cells may join and form a junction. As  shown in Figure 1, three kinds of cell junctions are recognized: Desmosomes  are protein attachments between adjacent cells. Inside the  plasma membrane, a desmosome bears a disk-shaped structure from which  protein fibers extend into the cytoplasm. Desmosomes act like spot welds to  hold together tissues that undergo considerable stress (such as skin or heart  muscle). Tight junctions  are tightly stitched seams between cells. The junction 
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Unformatted text preview: completely encircles each cell, preventing the movement of material between the cell. Tight junctions are characteristic of cells lining the digestive tract, where materials are required to pass through cells (rather than intercellular spaces) to penetrate the bloodstream. Gap junctions are narrow tunnels between cells that consist of proteins called connexons. The proteins allow only the passage of ions and small molecules. In this manner, gap junctions allow communication between cells through the exchange of materials or the transmission of electrical impulses. Figure 1. The three types of cell junctions....
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Cell Junctions - completely encircles each cell, preventing...

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