Exam 3 Review:  Chapter 23:  Bile & Biliary Tree

bile canaliculi - The minute channels which run between hepatocytes, and into which they secrete bile; they form the smallest and most distal branches of the biliary tree and carry bile toward the periphery of the lobules of the liver where it is collected into interlobar bile ducts at the "hepatic triad."  aka - bile capillaries

hepatic ducts - Any portion of the biliary tree; especially, the larger duct(s) which carry the bile from the lobes of the liver to the cystic and common bile ducts; they are lined by columnar epithelium and a delicate layer of smooth muscle.

cystic duct - The portion of the biliary tree which conveys bile to the gall bladder from the liver via the hepatic ducts between meals and from the gallbladder to the common bile duct (and on to the duodenum) during the intestinal phase of the digestion of a meal; it is lined by columnar epithelium and a delicate layer of smooth muscle.

common bile duct - The portion of the biliary tree formed by the union of the cystic duct and the hepatic duct which carries bile from the liver and the gallbladder to the duodenum during the intestinal phase of the digestion of a meal; it is lined by columnar epithelium and a delicate layer of smooth muscle.

gallbladder - The small, pear-shaped sac, located under the right lobe of the liver, in which bile secreted by the liver is stored until needed by the body for digestion of a fatty meal; it is lined by columnar epithelium and a layer of smooth muscle innervated by the Vagus Nerve and responsive to CCK.

sphincter of hepatopancreatic ampulla - The ring of smooth muscle which guards the opening of the merged common bile duct and pancreatic duct located in the wall of the duodenum; it is innervated by the Vagus Nerve and responsive to CCK.

bile - A bitter, alkaline, viscous, brownish-yellow or greenish-yellow mucous fluid which is secreted by the liver hepatocytes, collected into bile canaliculi and delivered by the biliary tree to be stored in the gallbladder, and discharged into the duodenum; it contains bile salts and bile acids which aid in the emulsification of ingested fats to improve the efficiency of lipid digestion and absorption; it also contains a variety of wastes such as bilirubin from the breakdown of the heme in hemoglobin and various bile pigments; adult humans produce 0.4 - 0.8 L daily.

bile salts and bile acids - A group of amphipathic (both lipid and water soluble) metabolic waste products of the hepatic catabolism of cholesterol and steroid hormones; they are produced by hepatocytes and added to bile; in bile they function as a surfactant to emulsify ingested fats to improve the efficiency of lipid digestion and absorption in the duodenum; they are reabsorbed into the bloodstream from the small intestine and returned to the liver by the hepatic portal circulation ("enterohepatic circulation") where they are recycled so that each molecule is used approximately 20 times; they also play a negative-feedback regulatory role in the control of hepatic synthesis of cholesterol.

emulsification - To make a preparation of one liquid (discontinuous phase) distributed in small globules or droplets throughout the volume of a second liquid (continuous phase); when water is the continuous phase, the preparation is termed a water emulsion, when a nonpolar liquid (oils, lipids, etc.) is the continuous phase, the preparation is termed an oil or lipid emulsion; bile, especially the bile salts and bile acids acting as a surfactant coating, contribute to the emulsification of ingested fats to improve the efficiency of lipid digestion and absorption in the duodenum.

bilirubin - An orange-yellow lipid pigment excreted by the liver into the bile which forms as a by-product of hemoglobin breakdown and recycyling; excess amounts in the blood or deposited in tissues produce the yellow appearance observed in jaundice.

17.  the functions of bile.

          (1)  provides some bicarbonate ions to assist in buffering acidic chyme transferred from the stomach to the duodenum
          (2)  contains bile salts and acids which act as emulsifiers to assist in lipid digestion
          (3)  provides a route of excretion for various wastes, in particular, bilirubin from heme degradation