[Morphological changes of the hamster gallbladder in the contracted and distended states]

The hamster gallbladders were investigated to clarify the morphological changes in the contracted and distended states. 1) The mucosal surface showed the highly convoluted folds in the contracted state, and the flat structure in distended state. 2) The height and width of mucosal epithelial cells were changed in correspondence with the contracted and distended state of the gallbladder. 3) A subepithelial blood capillary formed a well developed network, and possessed many pores opening mainly toward the mucosal epithelial cell. Three-dimensional structure of blood capillary was closely related to the morphological changes of the mucosal fold. 4) A contraction of distention of muscle layer of the gallbladder produced concomitant widening or narrowing of the lymphatic vessel lumen. It is suggested that muscular contraction worked as a "pump" for the lymphatic flow. 5) Smooth muscle cells in the muscle layer had many cell-to-cell junctions, but few neuromuscular junctions. It seems that there is a complicated interaction between nervous and humoral control mechanisms.