Light micrograph of gallbladder epithelium. The gallbladder is probably the most typical example of a simple columnar epithelium. It has tall cells, with a nucleus located in the basal third, at the same height in all cells. At the apical edge there is an increase in density, little evident at this magnification, which corresponds to a border of microvilli, less developed and ordered than the striated plate of the enterocytes. Below the epithelium, constituting the axis of the folds of the mucosa, is the connective tissue of the lamina propria.