Liver and Biliary Secretions PDF - European University Cyprus

Liver and biliary secretions Konstantinos Ekmektzoglou MD, PhD, FEBGH Assistant Professor School of Medicine European University Cyprus OCTOBER 2024 Biliary Liver tree BILE Secreted by the liver ~ 600 - 1000 ml/day IMPORTANT FOR 2 REASONS 1. fat digestion and absorption by emuls...

Liver and biliary secretions Konstantinos Ekmektzoglou MD, PhD, FEBGH Assistant Professor School of Medicine European University Cyprus OCTOBER 2024 Biliary Liver tree BILE Secreted by the liver ~ 600 - 1000 ml/day IMPORTANT FOR 2 REASONS 1. fat digestion and absorption by emulsification of large fat particles of food into many minute particles ► the surface of which can then be attacked by lipase enzymes secreted in pancreatic juice 2. aid in absorption of the digested fat end products through the intestinal mucosal membrane BILE ALSO IMPORTANT BECAUSE bile serves as a means for excretion of several important waste products from the blood Bilirubin (an end product of hemoglobin destruction) excesses of cholesterol  H2O and large portions of the electrolytes (except Ca) are reabsorbed by the gallbladder mucosa BILIARY SECRETION  BILIARY SECRETION In its course through the bile ducts, a second portion of liver secretion is added to the initial bile This additional secretion is a watery solution of Na and HCO3 ions secreted by epithelial cells that line the ductules and ducts Increases the total quantity of bile by as much as 100% Stimulated by secretin, which causes release of additional quantities of HCO3 ions to supplement the HCO3 ions in pancreatic secretion (for neutralizing acid that empties into the duodenum from the stomach) BILE STORED IN THE GALLBLADER The gallbladder can hold up to 30-60 ml of bile BUT IN 12 hours usually about 450 ml can be stored in the gallbladder because water, sodium, chloride, and most other small electrolytes are continually absorbed through the gallbladder mucosa ▼ END RESULT CONCENTRATED BILE (bile salts, cholesterol, lecithin, and bilirubin) Most of this gallbladder absorption is caused by active transport of Na through the gallbladder epithelium followed by secondary absorption of chloride ions, water, and most other diffusible constituents BUT WHAT Stimulates Gallbladder Emptying? when fatty foods reach the duodenum about 30 minutes after a meal  The gallbladder is also stimulated less strongly by acetylcholine- secreting nerve fibers from both the vagi and the intestinal enteric nervous system They are the same nerves that promote motility and secretion in other parts of the upper GI tract WHY DO WE NEED BILE?  SALTS OF THESE ACIDS ARE SECRETED IN THE BILE BILE SALTS USED FOR 2 THINGS Form small physical complexes with these lipids called micelles Detergent action on the fat Help in the absorption of particles in the food 1. Fatty acids 2. Monoglycerides 3. Cholesterol 4. Other lipids from the GI tract emulsifying or detergent function (BREAKING DOWN FAT GLOBULES INTO MINUTE SIZES) BLOOD IS IT IMPORTANT? IF NO BILE SALTS up to 40% of the ingested fats lost into the faeces metabolic deficit because nutrient loss ENTEROHEPATIC CIRCULATION WHAT REGULATES BILIARY SECRETION? A SMALL PREVIEW FOR NEXT YEAR – JUST TO MAKE THE CONNECTION The amount of cholesterol in the bile is determined partly by the quantity of fat that the person eats, because liver cells synthesize cholesterol as one of the products of fat metabolism in the body For this reason, people who consume a high-fat diet over a period of years are prone to development of gallstones Biliary Liver tree Portal hypertension Portal Hypertension Physiologic porto-systemic anastomoses. Portal circulation in blue, systemic circulation in green From Moubarak et al. Abdominal Imaging 2012 in SpringerImages database (non-commercial use permitted) Figure 2. Microscopic Anatomy of the Liver. The liver receives oxygenated blood from the hepatic artery and nutrient-rich deoxygenated blood from the hepatic portal vein. From Trowers and Tischler Gastrointestinal Physiology 2014 in SpringerImages database (non-commercial use permitted) THANK U!!!