Intrahepatic peribiliary glands of humans. I. Anatomy, development and presumed functions

The intrahepatic biliary tree is regarded as an excretory duct of two secretory units: hepatocytes and intrahepatic peribiliary glands. This review describes the anatomy, development and presumed functions of the latter. These glands are preferentially located around the intrahepatic large bile ducts, and are histologically divided into intramural and extramural structures. The former consist of simple tubular glands with much mucin, and are sparsely and irregularly distributed within the ductal wall. The latter are characterized by the presence of excretory units that consist of seromucinous acini and a conducting system in the periductal tissue. Pancreatic exocrine acini are occasionally admixed with extramural glands. These peribiliary glands appear in the late fetal period and complete their development about 15 years after birth. Extramural and intramural glands secrete neutral and acid mucin into the ductal lumen. Extramural glands contain several enzymes for digestion of protein and lipids. Neural and vascular supply of these glands may be related to the regulation of their secretion. Specific and non-specific immune responses within this glandular system may also be essential in the sterility of bile.