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Cell junctions

Cell junctions are molecular structures between cells that stabilize the tissue, form barriers and allow for transport of molecules between two cells.

The largest cell junctions are called desmosomes. They are protein complexes that connect the keratin fibers of two cells like a hook-and-loop fastener. Desmosomes help the tissue to resist shearing forces.

Tissues that form a barrier, such as the intestinal epithelium, require individual cells to be tightly connected to prevent any liquid escaping. This sealing function is performed by a network of tight junctions. These strands of protein complexes connect the plasma membrane of two neighboring cells forming a virtually impermeable barrier to fluid.

The tight junctions are supported by the adherens junctions. Adherens junctions are anchor-like protein complexes similar to desmosomes, but they are linked to the actin cytoskeleton.

Illustration of intestinal epithelium cells and the cell junctions between them. The illustration shows an example of a tight junction, an adherens junction, and a desmosome junction. The tight junction is illustrated by two purple colored plasma membranes that are connected by multiple green colored protein complexes. The Adherens junction is illustrated as two purple colored plasma membranes that are connected by multiple green cadherin molecules that are linked to yellow colored actin filaments, by linking proteins. The desmosome is illustrated as two purple colored plasma membranes that are connected by green colored cadherin molecules through a red colored attachment plaque. Long orange and yellow colored keratin molecules are attached to the attachment plaque, which reach into the intracellular space.

Figure 1: Cell junctions and their location in the intestinal epithelium.

Referred from:

Article
Intestinal epithelium