![]() ![]() Migratory cells of the immune system, such as neutrophils, use polarization for short-distance communication. Nature Reviews Molecular Cell Biology, 9(11), 887-901. From cells to organs: Building polarized tissue. To learn how they get these different proteins, see our Maintenance of polarity & regulation of membrane trafficking section.Īs explained in the section “ What is Polarity?” epithelial cells display apico-basal polarity, as well as specialized lateral membranes which allow for specialized diffusion/absorption of ions, secretion, and adhesion between cells (Figure 4). In each case, the apical and basolateral parts of the membrane are doing two different sets of functions, which require them to have different sets of membrane proteins. Absorptive cells, on the other hand, must import food molecules through their apical surface, before exporting the cells through their basal surface into the underlying tissue. The asymmetrical organization of the cells’ Golgi apparatus, secretory vessels and cytoskeleton enable them to discharge the mucus from their apical surface, which is the surface lining the gut. Goblet cells main role is to produce mucus to protect and lubricate the gut. Although both types of cells are classified as simple columnar cells, their differing polarity results in their different functional capabilities. One example of this differentiation can be seen in goblet and absorptive cells in the small intestine (Figure 3). Polarity varies according to cell type and leads to different functional usage. Different types of cells in the small intestine, which each have different functions. Image from: Alberts, B., Bray, D., Hopkin, K., Johnson, A., Lewis, J., Raff, M., et al. In addition, epithelial cells have lateral membranes, which are often characterized by tight junctions, gap junctions, and other cell-cell interactions which help to form epithelial tissue.įigure 1.Side view of an epithelial cell, displaying apico-basal polarity The basolateral region is the side that is below the tight junctions and contains the basolateral membrane which is in contact with the basal lamina. The apical region is defined as the area lying above the tight junctions (to learn more about tight junctions, click here) and contains the apical membrane which faces the lumen or the outer surface. In epithelial cells, the individual cells are split into two regions, the apical and basolateral regions, which are chemically and structurally different from each other (Figure 1). Differentiation in the ways these parts are asymmetrically organized helps to determine cell function and cell type. These characteristics are then maintained through cell division. In cells, polarity refers to the asymmetric organization of different aspects of the cell including the cell surface, intracellular organelles and the cytoskeleton. ![]()
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