An electron microscope study of developing bile canaliculi in the rat,

The development of bile canaliculi and the sequence of appearacne of iculi appear on about the thirteenth embryonic day in close association with linear attachment zones between adjacent hepatic cells. These canaliculi are formed by only two apposed cell surfaces and the configuration of a central biliary lumen bounded by 4– contiguous cells described classically as typical for developing mammalian liver is not apparent until day 16 or 17. The enlarged biliary spaces apparently arise as separate vesicles or saccules which subsequently elongate into tubules and interconnect. Evidence obtained in this study supports the concept that terminal bile ductules develop by direct transformation of tubular channels lined by hepatic cells under the influence of periportal connective tissue. Pericanalicular bodies develop in association with an hypertrophied Golgi zone. The sequence of appearance is: multivesicular bodies, microbodies, typical lysosomes. There is no evidence from this study that microbodies are related to differentiating mitochondria but the chronology of appearance suggests a close relationship to lysosomes.