3.3: Cell-to-Cell Junctions Hold Cells Together In Tissues
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Cell-to-Cell Junctions Hold Cells Together In Tissues
As stated in the introduction, a single cell is analogous to a single brick in a brick wall. Cells attach to one another to from tissues. There are different types of cell-to-cell attachments helping to hold cells together. The types of cell-to-cell attachments or junctions present in a tissue is related to the functions of that tissue. There are three main cell-to-cell junctions discussed below: tight junctions, desmosomes, and gap junctions.
A tight junction is a watertight seal between two adjacent animal cells. The proteins that make up tight junctions tightly hold the cells against each other.
This tight adherence prevents materials from leaking between the cells; tight junctions are typically found in epithelial tissues that line internal organs and cavities, and comprise most of the skin. For example, the tight junctions of the epithelial cells lining your urinary bladder prevent urine from leaking out into the extracellular space.
Desmosomes act like spot welds between adjacent epithelial cells. Cadherins, short proteins in the plasma membrane, connect to intermediate filaments to create desmosomes. The cadherins connect two adjacent cells to maintain the cells in a sheet-like formation in organs and tissues that stretch, like the skin, heart, and muscles.
Gap junctions are channels between adjacent cells that allow for transporting ions, nutrients, and other substances that enable cells to communicate. Gap junctions are particularly important in cardiac muscle. The electrical signal for the muscles to contract passes efficiently though gap junctions, allowing the heart muscle cells to contract in tandem.
- "Biology 2e" by Mary Ann Clark, Matthew Douglas, Jung Choi, OpenStax is licensed under CC BY-NC 4.0