Topics Discussed: biliary tract; congenital anomalies of the biliary tract, gallbladder and liver; gastroenterology and hepatology.
Sections: Ductal Plate Malformations, Bile Duct Paucity Syndromes, Extrahepatic Biliary Atresia, Gallstones and Gallbladder Disease, References.
Excerpt:"In the human embryo the first anlage of the bile ducts and liver
is the hepatic diverticulum from the proximal gastrointestinal tract,
as described in Chapter 418. The caudal part
of this bud, known as the pars cystica, grows in length and forms
the gallbladder, cystic duct and common bile duct. At about the
eighth week of gestation, the hepatic precursor cells that lie adjacent
to the hilar portal vein vessels form a sleeve-like double layer
of cells that extends toward the periphery along the smaller intrahepatic
portal vein branches. These hepatoblasts strongly expresses biliary
specific cytokeratins and can be considered biliary precursor cells,
that then form a continuous single-layered ring around the portal
mesenchyme, known as the ductal plate.1 Beginning
at 12 weeks of gestation and extending into the postnatal period,
the ductal plate undergoes progressive remodeling. As new ductules
form they are incorporated into the periportal mesenchyme that surrounds
the portal vein branches. Thus, during successive periods of fetal
life, ductal plate remodeling leads to the formation of the intrahepatic biliary
tree. The largest ducts are formed first, followed by segmental,
interlobular, and, finally, the smallest bile ductules. Arrest or derangement
in remodeling leads to the persistence of primitive bile duct configurations
termed ductal plate malformations. The occurrence of ductal plate
malformations at different generations of the developing biliary
tree gives rise to different clinicopathologic entities,..."
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