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4 - The Cholangiopathies
- from SECTION I - PATHOPHYSIOLOGY OF PEDIATRIC LIVER DISEASE
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- By Valeer J. Desmet, M.D., Ph.D., Professor, Department of Pathology, Katholieke Universiteit Leuven, Leuven, Belgium, Tania A. D. Roskams, M.D., Ph.D., Full Professor, Head of Liver Research Unit, Department of Morphology and Molecular Pathology, Katholieke Universiteit Leuven, Leuven, Belgium; Head of Clinics, Department of Pathology, University Hospital Leuven, Leuven, Belgium
- Edited by Frederick J. Suchy, Mount Sinai School of Medicine, New York, Ronald J. Sokol, University of Colorado, Denver, William F. Balistreri, University of Cincinnati
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- Book:
- Liver Disease in Children
- Published online:
- 18 December 2009
- Print publication:
- 07 May 2007, pp 35-70
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- Chapter
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Summary
EMBRYOLOGY OF EXTRA- AND INTRAHEPATIC BILE DUCTS, DUCTAL PLATE, AND DUCTAL PLATE MALFORMATION
Development of Extrahepatic Bile Ducts
In the human embryo, the first anlage of the bile ducts and the liver is the hepatic diverticulum or liver bud. It starts as a thickening of the endoblastic epithelium in the ventral wall of the cephalad portion of the foregut (the future duodenum), near the origin of the yolk sac; this area is termed the anterior intestinal portal. This occurs around the 7-somite (2.5-mm) stage on the 18th day. In the 19-somite (3-mm, 22nd-day) embryo the diverticulum is formed. In the 22-somite embryo, the hepatic diverticulum is a well-defined hollow structure. From the ventral and lateral surfaces of the diverticulum, on which the endoderm is in contact with the bulk of the mesoderm of the septum transversum (between the pericardial and peritoneal cavities), short sprouts of endodermal cells extend into the septum transversum to form the earliest anlage of the liver [1].
In the embryo about 5 mm in length, the diverticulum also shows a protruding bud in its distal part. Some investigators accordingly distinguish in the hepatic diverticulum a cranial part (pars hepatica) and a caudal part (pars cystica) [2].
The caudal bud or pars cystica grows in length and represents the anlage of the gallbladder, the cystic duct, and common bile duct (ductus choledochus). For up to 8 weeks of gestation, the extrahepatic biliary tree further develops through lengthening of the caudal part of the hepatic diverticulum.