The Gallbladder concentrates and stores bile, and sends it to the duodenum. An empty gallbladder presents numerous deep mucosal folds. It has a mucosa layer, and its epithelium is simple columnar with well developed microvilli, apical junctional complexes, apical and basal concentrations of mitochondria, and complex lateral plications. They closely resemble the absorptive cells of the intestine. It actively transports Na+ and Cl- (and HCO3-) from the cytoplasm to the intracellular compartment of the epithelium. Lateral transportation results in distention of the intercellular space (transportation of water).