The arterial supply of the common bile duct is derived from:
The majority of the blood flow to the human common bile duct originates from the right hepatic artery and gastroduodenal arteries, with major trunks running along the medial and lateral aspects of the common duct (often referred to as the 3 o'clock and 9 o'clock positions).
Anomalies of the hepatic artery and cystic artery are present in what percent of individuals:
Variations in the anatomy of the cystic and hepatic arteries are exceedingly common, the "classical" anatomy only appearing in 50 to 60% of the population. The cystic artery is a branch of the right hepatic artery in 90% of individuals. The most common arterial anomaly of the portal arterial system is a replaced right hepatic artery originating from the superior mesenteric artery; this happens in 20% of persons.
The treatment of choice for a type I choledochal cyst is:
Choledochal cysts are rare congenital cystic dilations of the extrahepatic and/or intrahepatic biliary tree. Females are affected three to eight times more commonly than men. Though they are commonly diagnosed in childhood, as many as one half of patients are not diagnosed until adulthood. The most common presentations in adulthood are jaundice and cholangitis, and less than one-half of patients present with the classic clinical triad of abdominal pain, jaundice, and a mass. Ultrasonography (US) or computed tomographic (CT) scanning will confirm the diagnosis, but a more definitive imaging technique such as endoscopic retrograde cholangiopancreatography (ERCP), percutaneous transhepatic cholangiography, or magnetic resonance cholangiopancreatography (MRCP) is required to assess the biliary anatomy and plan the appropriate surgical treatment. The risk of cancer development in these patients is up to 1 5%, and can largely be mitigated by excision of the biliary tree. Types I, II, and IV cysts are treated with excision of the extrahepatic biliary tree with a Roux-en-Y hepaticojejunostomy. Type IV may also require a segmental liver resection. Sphincterotomy is recommended for type III cysts.
Relaxation of the sphincter of Oddi in response to a meal is largely under the control of which hormone?
The sphincter of Oddi is a complex structure that is functionally independent from the duodenal musculature and creates a high-pressure zone between the bile duct and the duodenum. The sphincter of Oddi is about 4 to 6 mm in length and has a basal resting pressure of about 13 mm Hg above the duodenal pressure. On manometry, the sphincter shows phasic contractions with a frequency of about 4/min and an amplitude of 12 to 140 mm Hg. The spontaneous motility of the sphincter of Oddi is regulated by the interstitial cells of Cajal through intrinsic and extrinsic inputs from hormones and neurons acting on the smooth muscle cells. Relaxation occurs with a rise in cholecystokinin (CCK), leading to diminished amplitude of phasic contractions and reduced basal pressure, allowing increased flow of bile into the duodenum. During fasting, the sphincter of Oddi activity is coordinated with the periodic partial gallbladder emptying and an increase in bile flow that occurs during phase II of the migrating myoelectric motor complexes.
What percentage of the bile acid pool is reabsorbed in the ileum through the enterohepatic circulation?
Bile is mainly composed of water, electrolytes, bile salts, proteins, lipids, and bile pigments. Sodium, potassium, calcium, and chlorine have the same concentration in bile as in plasma or extracellular fluid. The pH of hepatic bile is usually neutral or slightly alkaline, but varies with diet; an increase in protein shifts the bile to a more acidic pH. The primary bile salts, cholate and chenodeoxycholate, are synthesized in the liver from cholesterol. They are conjugated there with taurine and glycine and act within the bile as anions (bile acids) that are balanced by sodium. Bile salts are excreted into the bile by the hepatocyte and aid in the digestion and absorption of fats in the intestines. In the intestines, about 80% of the conjugated bile acids are absorbed in the terminal ileum. The remainder is de-hydroxylated (de-conjugated) by gut bacteria, forming secondary bile acids deoxycholate and lithocholate. These are absorbed in the colon, transported to the liver, conjugated, and secreted into the bile. Eventually, about 95% of the bile acid pool is reabsorbed and returned via the portal venous system to the liver, the so-called enterohepatic circulation. Five percent is excreted in the stool, leaving the relatively small amount of bile acids to have maximum effect.
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