Cells in the body frequently need to stick together or communicate with one another. Animal tissues feature different types of cell junctions to meet structural and communication needs. Cell junctions are most frequently found in tightly packed epithelial tissues which line and cover all of the human body's surfaces.
Tight Junctions
- bind cells together tightly
- prevent leakage of extracellular fluid
- are composed of specific interlocking proteins
Tight junctions are also known as zona occludens, which means "belt that shuts off." Functionally, tight junctions hold cells closely together to prevent leakage of extracellular fluid. In fact, epithelial cells are so closely linked by tight junctions that some proteins from neighboring cell membranes fuse. Though tight junctions can bind cells together very tightly, they can also connect loosely enough to let small ions through. The degree of tightness in cell junctions depends on what type of cell they hold together. Overall, tight junctions help to seal cells together.
