GI Lecture 5 - Pancreatic and Biliary Secretion

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  • Created by: LBCW0502
  • Created on: 06-10-19 15:13
Outline the organisation of the pancreas (1)
Pancreas (common bile duct, main pancreatic duct). Lobules (secretory units), intralobular ducts. Intercalated duct. Pancreatic duct epithelial cell, centroacinar cell, pancreatic acinar cell. Acinus
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Outline the organisation of the pancreas (2)
Pancreatic acinar cell (zymogen granules, golgi, mitochondria, RER). Pancreatic duct epithelial cell (mitochondria)
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Outline the cephalic, gastric and intestinal phases of digestion (1)
Cephalic phase (20% of total) - sight, smell, taste of food, chewing, parasympathetic vagal activity, secretion of ACh, VIP by nerve endings
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Outline the cephalic, gastric and intestinal phases of digestion (2)
Gastric phase (10% of total). Distension of stomach, vago-vagal reflex, secretion of gastrin by G cells of antrum
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Outline the cephalic, gastric and intestinal phases of digestion (3)
Intestinal phase (70% of total). Products of protein and fat digestion in duodenum, secretion of CCK by I cells. Low pH of duodenum, secretion by secretin by S cells
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Outline the cephalic, gastric and intestinal phases of digestion (4)
All results in enzyme-rich secretion by acinar cells. Secretion of bicarbonate-rich fluid by duct cells. Pancreatic juice
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Outline how amino acids are incorporated into zymogen granules
Amino acids, produced in RER, modified in Golgi. In condensing vacuoles. Incorporated into zymogen granules
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Describe the secretion of pancreatic juice (1)
Highest rate of protein synthesis of any secretory tissue with exception of lactating mammary gland. Aqueous component rich in bicarbonate which neutralises duodenal content and enzyme component
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Describe the secretion of pancreatic juice (2)
Proteolytic enzymes, tripsinogen, chymotrypsinogen, procarboxypolypeptidase, ribonuclease, deoxyribonuclease. Amylase (starch, glycogen). Lipase (hydrolysis neutral fat into glycerol and fatty acids
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Describe the secretion of pancreatic juice (3)
CCK-PZ causes contraction of gallbladder, secretion of bile salts. Electrolyte concentrations in pancreatic juice - constant Na, high bicarbonate, low Cl and low K
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Describe pancreatic secretions in the intestinal phase (1)
Protein and lipid breakdown products stimulate vagovagal reflex that stimulates primarily the acinar cells. H+ stimulates S cells into duodenum to secrete secretin which acts on receptors on duct cells stimulating bicarbonate secretion
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Describe pancreatic secretions in the intestinal phase (2)
Protein and lipid breakdown products stimulate I cells in duodenum to secrete CCK which acts on receptors on acinar cells, stimulating enzyme secretion
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Describe the neural and hormonal stimuli that promote production and release of bile (1)
Parasympathetic impulses along vagus nerves stimulate bile production by liver. Acidic chyme entering duodenum stimulates secretion of secretin into blood. Fatty acids/amino acids in chyme stimulate secretion of CCK into blood
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Describe the neural and hormonal stimuli that promote production and release of bile (2)
CCK causes contraction of gallbladder. Secretin enhances flow of bile rich in bicarbonate from liver
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Describe the relationship between bile flow and liver blood flow and the role of oxygen delivery on bile flow
Increase blood flow results in increase in bile flow (increase in oxygen levels)
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Describe the relationship between biliary pressure and blood pressure
Increase in blood pressure leads to increase in bile pressure (not due to hydrostatic pressure)
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Outline the structure of biliary system and storage of bile salts in gallbladder (1)
Liver lobule, terminal bile ducts, canaliculi, perilobular bile duct, interlobular bile duct. Hepatocytes. Bile flow. Left hepatic duct, common hepatic duct, common bile duct, pancreatic duct. Cystic duct. Right hepatic duct. Gall bladder. Duodenum
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Outline the structure of biliary system and storage of bile salts in gallbladder (2)
Ampulla (of Vater). Sphincter of Oddi. Pancreatic duct
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Which ions are present in the gallbladder containing bile?
Cl and Na (and H2O)
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Describe the absorption of lipids (1)
High concentrations of bile salts and fats spontaneously form micelles. Co-lipase enables lipase to break down fats. Fatty acids and monoglycerides diffuse into epithelial cells. These are synthesised into triglycerides in SER
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Describe the absorption of lipids (2)
In Golgi, fats are combined with protein to form chylomicrons. Vesicles containing chylomicrons extruded from the cell enter lacteal. Chylomicrons transported away in lymph
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Summarise fat digestion and absorption (1)
Fats emulsified by bile salts and lecithin. Pancreatic lipases break down fat into fatty acids, monoglycerides and glycerol. Fatty acids and monoglycerides enter epithelial cells by diffusion, form chylomicrons and enter lymphatic circulation.
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Summarise fat digestion and absorption (2)
Glycerol and small chain fatty acids absorbed into capillary blood in villi and into portal circulation to the liver
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Outline the composition of bile
Electrolytes, bile acids, fatty acids, bilirubin, phospholipids, cholesterol, proteins
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Outline bilirubin secretion in liver cells
Bilirubin unbinds from albumin in the blood. Diffusion into liver cell. Formation of conjugated bilirubin (use of glucuronyl transferase, UTP and glucose, UDP glucuronic acid). UDP produced. Conjugated bilirubin enters bile canaliculus
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Outline the transport in bile formation
Bilirubin with water, conjugated bile acids, inorganic ions, bicarbonate enter into bile ductule, formation of bile
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What is the enterohepatic circulation of bile acids? (1)
Bile acids delivered by liver to duodenum are conjugated. Vast majority are reabsorbed as conjugated bile salts in the terminal ileum via Na coupled co-transporter. Bile salts can also form bile acids in the terminal ileum
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What is the enterohepatic circulation of bile acids? (2)
Absorbed bile acids return to the liver via portal blood and are taken up into the hepatocyte for re-secretion
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Describe the absorption of fluid
By the time the meal reaches the SI, the volume has increased from 2000 mL to 9000 mL. The SI and colon then reabsorb fluid until only 150 mL is excreted in faeces
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Other cards in this set

Card 2

Front

Outline the organisation of the pancreas (2)

Back

Pancreatic acinar cell (zymogen granules, golgi, mitochondria, RER). Pancreatic duct epithelial cell (mitochondria)

Card 3

Front

Outline the cephalic, gastric and intestinal phases of digestion (1)

Back

Preview of the front of card 3

Card 4

Front

Outline the cephalic, gastric and intestinal phases of digestion (2)

Back

Preview of the front of card 4

Card 5

Front

Outline the cephalic, gastric and intestinal phases of digestion (3)

Back

Preview of the front of card 5
View more cards

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