Cell connections. So how are cells connected to one another? Well, there are three major types of cell connections.
Desmosomes, which include spot desmosomes, belt desmosomes, and hemidesmosomes, and gap junctions and tight junctions. Spot desmosomes look like spot welds holding adjacent cells together, and they're composed of several different proteins. Here we have two adjacent cells.
Their plasma membranes are here, and on the internal surface of their plasma membranes, is what is called a protein plaque. Protein filaments extend from the protein plaque in both cells through the plasma membrane and anchor to one another outside of the cell. Inside each of the cells, intermediate filaments, which are part of cell cytoskeleton, anchor to the protein plaque. This cell connection arrangement provides support to the cells. Belt desmosomes are also centered around a protein plaque on the inside of the plasma membrane.
From this plaque, proteins extend out and anchor to one another like in spot desmosomes. Gap junctions are channels that form when the plasma membranes of adjacent cells connect. Membrane proteins form fluid-filled tunnels called connexons that allow certain substances and impulses to pass from one cell to another. Tight junctions are formed from plasma membrane proteins connecting one cell to another. They prevent substances from passing between the cells requiring substances to pass through a cell.
This allows for protection of other body structures. Hemidesmosomes are similar to spot desmosomes in that they consist of intermediate filaments connected to a protein plaque with protein filaments extending outward and connecting the cell to another body structure. And that be the basics on cell connections.