Flashcards in Pancreas and Liver Deck (31):
What is the role of the exocrine pancreas and liver?
+ Accessory organs for intestines
- provide excretions (digestive enzymes, HCO3) directly into intestine lumen, to digest CHO, protein, lipid in small intestine
What are the physical features of the pancreas?
+ Lies retroperitoneal (except tail), close to major blood vessels, difficult to access
+ Lies in C-shaped curve of duodenum with a head, neck, body, tail and uncinate process
Where does the pancreatic blood supply come from?
+ Mainly via the splenic artery (from coeliac trunk)
+ Pancreatico-duodenal arteries (from SMA (superior mesenteric artery) or coeliac trunk)
What are the primary functions of the exocrine pancreas?
+ Neutralise acid; digestive pro-enzymes secreted via pancreatic duct to 2nd part of duodenum
+ Deliver enzymes for macronutrient digestion in duodenum
What are the acinar cells of the pancreas?
+ Main secretory cells
+ Clusters are connected by intercalated ducts
+ Converge on collecting ducts
+ Lining cells add ions and secretions
What are the phases of digestion that exocrine pancreas regulation is dependent on?
What is involved in the cephalic phase of digestion?
Vagus nerve stimulates pancreatic secretions by releasing ACh and VIP
What is involved in the gastric phase of digestion?
Medicated by vagovagal reflexes
What is involved in the intestinal phase of digestion?
Controlled hormonally by secretin (in response to H+) and CCK (in response to aas, fatty acids, monoacylglycerols)
What are the secretory cells involved with the exocrine pancreas?
+ Acinar cells
+ Ductal cells
What is the role of zymogen granules, and where are they found?
+ They house inactive (and active) digestive enzymes
+ Secreted in respins to CCK (& VIP, gastric-releasing peptide)
+ Found in acinar cells
What happens to zymogen granules upon activation?
They are exocytosed from acinar cells into luminal space
What are features of acinar cells?
+ Basolateral CCK & ACh binding stimulates Cl- transport across apical mambrane.
+ Facilitates paracellular Na+ & water movement
What are features of ductal cells?
+ Secretin & ACh bind in ductal cells
+ Activates cystic fibrosis transmembrance conductance
regulators, Cl- channels, Cl-HCO3- co-transporters.
+ Transporters recycle Cl- and HCO3-
What is the effect of pancreatic secretion flow rate?
+ Alters ionic conentration: increased flow rate = HCO3- conc. increased, Cl- conc. decreased
+ Na+ and K+ conc. are not affected by flow rate
What are the non-biliary liver functions?
+ Metabolism: pf CHO, protein, fat
- stores/releases CHO i.e glycogen (glycogenolysis, gluconeogenesis)
- removal of ammonia and ethanol + drug biotransformations
- produces large amount of lymph
+ Immune system functions:
- removal of intestinal bacteria from portal blood so there is none in systematic circulation
What are features of the liver?
+ Lies across the upper abdomen, under the diaphragm
+ Surrounded by peritoneum except for the bare area (related to diaphragm posteriorly)
+ May be palpable below the costal margin
+ Deep to its peritoneal covering, liver is completely surrounded by Glisson's capsule
What is Glisson's capsule?
+ A thin connective tissue layer that sends extensions into the organ, inbetween the lobules
+ Not strong enough to hold sutures that may be required following trauma to the liver
By which structures is the liver supplied?
+ Hepatic portal vein brings absorbed nutrients from stomach and gut
+ Hepatic portal artery supplies hepatocytes (liver cells) with oxygen
How is bile drained from the liver?
+ Hepatocytes secrete bile into canaliculi, across series of bile ducts until they form the common hepatic duct
+ Bile flow from hepatocytes is in OPPOSITE direction of blood from hepatic artery and portal vein
Via what structure is venous drainage?
Via hepatic veins that enter the inferior vena cava
Describe the structure of the liver?
+ Left and right lobes (separated by falciform ligament)
+ Quadrate lobe next to gall bladder
+ Posterior surface shows caudate lobe next to IVC
+ Bare area is diaghragmatic surface of liver (no peritoneal covering)
What are all of the functions of the liver?
+ Synthesis and secretion of bile
+ Storage (of glucose, glycogen, proteins, vitamins and fats)
+ Detoxification (of metabolic waste)
+ Synthesis of blood clotting (and anticoagulant factors (fibrinogen & prothrombin))
What are some features of bile?
+ Bile pigments are derived as the breakdown products of haemoglobin; Kupffer cells (fixed phagocytes) play a role in their formamtion
+ Bile salts responsible for detergent and emulsifying effect of bile on fats
+ Increase absorption of fats by small intestine
What are the constituents of bile?
+ Bile pigments (chiefly bilirubin)
+ Fatty acids
What are relations of liver between neighbouring structures?
+ Right kidney and suprarenal gland
+ Diaghpragm with lungs and pleura above (superior)
+ Stomach, duodenum (posterior)
+ Abdominal wall and ribcage (anterior)
+ Hepatic fixture and transverse colon
+ Gallbladder and portal triad
How does the hepatobiliary system function?
+ Bile goes from common bile duct into duodenum or gallbladder
+ Sphincter of Oddi controls path into small intestine:
- contracted: gallbladder contraction forces bile down common bile duct
- relaxed: bile flows down common bile duct to duodenum
+ Sphincter relaxation regulated primarily by CCK
What is the function of the gallbladder?
+ Stores and distributes bile - in concentrated form
+ Contracts to ecpel bile in response to CCK (same as Sphincter of Oddi to relax)
+ Vagal stimulation causes weak gallbladder contraction
+ Somatostatin & noradrenaline inhibit bile acid secretion
What does exocrine pancreas regulation occur via?
+ Via stimulatory effects of secretin and CCK
+ Via inhibitory effetcs of somatostatin
What is storage/secretion of substrates by the liver dependent upon?
The fed/fasted state