ABSTRACT
The present study was performed to thorough the light on the fine structure of the gall bladder epithelium where there is no available literatures on this respect in guinea pig. This study was carried out on ten adult guinea pigs. They were sacrificed and the gall bladders were removed and were cut into different regons.The specimems were divided into small pieces for parafin sections and very small pieces immersed in glutaraldehyde for E/M. From the ultrastructural study, it can be concluded that: the lining epithelium is composed of ordinary epithelial [clear] cells, pencil [dark] and basal cells. The first two types of cells possess microvilli on their luminal surface. The apical ends of the lateral walls appear denser than the basal segments due to the presence of tight junctions. The lateral cell walls show infolded membranes. The basal plasma membrane is attached to the lamina propria by peg - and-socket interdigitations.The gall bladder epithelium of guinea pig is capable of actively secreting mucus droplets and do so as a merocrine secretion.The cytoplasm presents cuticular, subcuticular, supranuclear, nuclear and basal zones. Large dense and stippled granules are found in the subcuticular zone. Also, the cytoplasm contains mitochondria and endoplasmic reticulum, mainly in the subcuticular zone.The guinea pig has a well developed gall bladder, much similar to that of man