các đơn vị, acini, được bố trí như ống, mỗi xung quanh một tĩnh mạch trung tâm perfused bởi một chi nhánh của tĩnh mạch cửa. Tế bào gan và một hệ thống xoang tỏa ra từ mỗi tĩnh mạch trung tâm trong một tế bào gan mỗi perfused trên hai cạnh của nó bằng chất lỏng hình sin (hình 8-17). | 318 PDQ PHYSIOLOGY Anatomy of the biliary system. The liver is composed of microcirculatory units the acini that are arranged like tubes each around a central vein that is perfused by a branch of the portal vein. Hepatocytes and a system of sinusoids radiate from each central vein in such a way that each hepatocyte is perfused on two of its sides by sinusoidal fluid Figure 8-17 . Sinusoid Hepatocytes Central portal venule Bile canaliculus H Tight junction BA ATP H Sinusoidal space space of Dissé Na A- X- C Na H2O Figure 8-17 Anatomy of the biliary system. Hepatocytes are arranged so as to form sinusoids that radiate from a central portal venule. Bile canaliculi lie between adjacent liver parenchymal cells hepatocytes . Bile formation is dependent on three types of ATPases in the canalicular membrane. Two of them are organic anion A- or cation C transporters and one transports bile acids BA . Each of them also transports a variety of drugs or hormones. The sinusoidal membrane also has three types of carriers identified as BA-Na A--X- and C -H . The Na -dependent bile acid carrier BA-Na transports conjugated bile acids and a number of hormones and drugs. A- -X- is a Na -independent anion exchanger system that will also transport unconjugated bile acids bilirubin the dye indocyanine green and others. C -H is a cation exchanger. HCO. ATP ATP ATP Na 3Na Chapter 8 Gastrointestinal System 319 The other two sides each enclose a system of canaliculi that connects to a system of ducts leading into the gallbladder. The canaliculi are the site of bile acid secretion from hepatocytes. Secretion of bile. Bile acids. Bile acids are the main metabolites of cholesterol. Cholesterol is either synthesized de novo from acetyl-CoA in hepatocytes see Figure 10-3 in Chapter 10 Metabolism and Nutrition or recycled from dietary cholesterol that enters hypotocytes mainly by endocytosis of chylomicron remnants see Fat Digestion and Absorption below . The liver continuously produces the .
