Pancreas and Liver Flashcards
What is the exocrine function of the liver and pancreas?
Act as an accessory organ for intestines by providing excretions directly into the luman of the small intestine
What is the endocrine function of the pancreas and liver?
Regulates blood borne energy substrate availability (such as glucose) via hormones
What makes the pancreas difficult to reach?
Its a reteroperitoneal organ which is surrounded by many major blood vessels.
Name the main blood supplies for the pancreas
The splenic artery (from the coeliac trunk) and the pancreatico-duodenal arteries. (from the superior mesenteric artery or the coeliac trunk)
Name the primary function of the exocrine pancreas
It secretes fluid that neutralises acid (secretions enter just after the stomach) and it delivers enzymes for macronutrient digestion in the duodenum.
Describe the features of acinar cells
They are the main secretory cells which are clustered around an intercalated duct , these intercalated ducts all converge into the intraglobular duct. Acinar cells also add ions to secretions.
The exocrine secretions of the pancreas are regulated depending on the stage of digestion. Explain how they are regulated at the different stages of digestion
Cephalic - Vagus nerve stimulates panreatic secretuins by releasing acetylcholine (ACh) and VIP.
Gastric - secretions are controlled by vasovagal reflexes
Intestinal - secretions controlled by secretin and CCK.
Describe the role of Zymogen granules in Acinar cells
They house inactive/actice digestive enzymes. They are secreted in response to CCK, VIP and gastrin-releasing peptide. With activation, zymogen granuels are exocytosed from acinar cells directly into the luminal space.
How is exocytosis of zymogen granuels controlled?
Hormonally or neurally
Where does ion secretion occur in the pancreas?
In Acinar cells and intercalated duct cells.
Explain how ions are added by acinar cells
Basolateral CCK and ACh binding stimulates Cl- transport across apical membrane. This facilitates the movement of sodium ions and water.
Explain how ion secretion occurs in intercalated ductal cells
Secretin and ACh bind in ductal cells which activates cystic fibrosis transmembrane conductance regulators, Chloride channels, chloride bicarbonate ion co-transporters. The transporters recycle chloride and bicarbonate ions.
Describe what happens when there us an increased flow rate of ionic concentration
Conc of bicarbonate ions increases but conc of chloride ions decreases. Potassium and sodium ion conc remains unaffected.
Describe the position of the liver in the abdomen
Lies across upper abdomen, under the diaphragm. It is surrounded by peritoneum except the bare area which may be palpable under the costal margin.
What supplies the liver with nutrients and where do they come from?
It is supplied by the hepatic portal vein which brings absorbed nutrients from the stomach and gut.
What supplies hepatocytes with oxygen?
The hepatic artery
How is bile drained?
Via canaliculi that lie between the hepatocytes into bile ductules and eventually into bile ducts.
What is the liver surrounded by?
Glisson’s capsule, this is a thin connective tissue with extensions into the organ between the lobules
Describe the structure of the liver
It has right and left lobes which are separated by the falciform ligament and a quadrate lobe next to the gall bladder.
Describe the functions of the Liver
Synthesis and secretion of bile, Storage of glucose, glycogen, proteins, vitamins and fats. Detoxification of metabolic waste, and synthesis of blood clotting and anticoagulant factors
What are the main constituents of bile?
Bile pigments (mainly bilirubin), cholesterol, phospholipids, fatty acids, water and electrolytes.
What are bile pigments made up from and what cells play a role in their formation.
Bile pigments are derived from the breakdown products of haemoglobin. Kupffer cells play a role in formation.
What allows for the absorption of fats across the intestine wall?
Bile salts. They are responsible for the detergent and emulsifying effect on fats since fats cannot be absorbed unless broken down and held in an emulsion.
what do bile ducts form?
The common hepatic duct
Describe the travel of bile and what controls its path
Bile goes from the common bile duct into the duodenum or the pancreas. This direction is controlled by the Sphincter of Oddi, if contracted the bile will enter the gallbladder, if relaxed it will travel mainly to the duodenum.
What is relaxation of the Sphincter of Oddi controlled by?
CCK.
Describe the role of the gallbladder and what causes it to secrete bile
Stores concentrated bile and distributes it. The gallbladder contracts in response to CCK and squeezes out bile. Vagal stimulation causes weak gallbladder contraction.
What inhibits bile acid secretion in the gallbladder
Somatostatin and noradrenaline
Name some of the non-biliary liver function?
Metabolism of glycogen, protein and fat. Detoxification, key in removing ammonia, ethanol and drugs. Also immune system function, it removes intestinal bacterial from portal blood so it isn’t circulated around the body.
