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Digestive System > Functions and Secretions of the Pancreas > Flashcards

Functions and Secretions of the Pancreas Flashcards

1
Q

What are the functions of the pancreas

A
  • Digestion of fats, proteins and nutrients by producing enzymes
  • Regulate environment for enzymatic digestion
  • Regulates both fed and fasted states (insulin and glucagon)
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2
Q

What is the ampulla of Vater

A
  • The swelling in the duodenal wall caused by the joining of the common bile duct and the main pancreatic duct
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3
Q

What structures drain into the main pancreatic duct

A
  • Intralobular duct
  • Interlobular duct
  • These form the ductular network which comes from the lobes of the pancreas
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4
Q

What forms the sphincter of Oddi and what is its function

A
  • Formed by thickening of muscular wall
  • Regulates ductal flow into duodenum and prevents reflux
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5
Q

What happens at the major duodenal papilla

A
  • Contents of the main pancreatic duct and common bile duct empty into the descending duodenum
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6
Q

What is the positional significance of the major duodenal papilla

A
  • Marks transition from foregut to midgut
  • Celiac trunk stops supplying thee gut, instead the superior mesenteric artery supplies the gut from this point.
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7
Q

What can be caused by blockage at distal end of common bile duct

A
  • Blockage of pancreatic duct
  • Eventually pancreatitis
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8
Q

What are the units of the pancreas that reside within the lobules called and what are they composed of

A
  • Functional secretatory units
  • Each composed of an acinus and a small intercalated duct
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9
Q

What is the acinus of the functional secretatory units

A
  • A cluster of acinar cells that make and secrete proteins into the lumen of the epithelial structure
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10
Q

What organelles make acinar cells suited to their function

A
  • RER
  • Secretatory granules
  • Exocytosis at apical pole
  • Specialised for production and secretion of large number of proteins
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11
Q

List some things that are secreted by pancreatic acinar cells

A
  • A plethora of zymogens (inactive enzyme precursors)
  • Digestive enzymes
  • Isotonic, bicarbonate rich, plasma like fluid (to accompany secretatory proteins to avoid obstruction)
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12
Q

What is a centroacinar cell

A
  • The very first cells of the intercalated duct and thus are located at the junction of the pancreatic acinar cells and duct cells.
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13
Q

What do pancreatic goblet cells do and why is this important

A
  • Produce mucus which is important for:
    > Lubrication
    > Hydration
    > Mechanical protection of surface epithelial cells
    > Immunologic role
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14
Q

What stimulates acinar cells to produce zymogen and through what pathway

A
  • Ach - from vagal stimulation
  • CCK - I cells (specialised cells that line the small intestine, stimulated by fat in food
  • Through the PLC/ PKC/ Ca 2+ single transduction pathway
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15
Q

What other than pancreatic acinar cells does CCK stimulate and why

A
  • Gall bladder contraction
  • Pumps bile into small intestine to emulsify fat, only emulsified fat can be broken down by lipase
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16
Q

What do pancreatic duct cells produce and why

A
  • Bicarbonate ions
  • Prevent peptic ulceration
  • Neutralise acidic conditions
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17
Q

How is the bicarbonate ion made in the pancreatic duct cells

A
  • Water and carbon dioxide makes carbonic acid which dissociates into a bicarbonate ion and a proton
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18
Q

How do pancreatic duct cells counteract the alkaline tide of the stomach

A
  • The bicarbonate ion remains in the lumen to neutralise stomach acid where as the proton is pumped into the blood neutralising the alkaline tide.
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19
Q

How do pancreatic duct cells counteract the alkaline tide of the stomach

A
  • The bicarbonate ion remains in the lumen to neutralise stomach acid where as the proton is pumped into the blood neutralising the alkaline tide.
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20
Q

What stimulates pancreatic duct cells to produce bicarbonate ions

A
  • Ach - vagal stimulation
  • Secretin - S cells in the small bowel (stimulated by acid coming from the stomach)
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21
Q

How do Ach and secretin stimulate the pancreatic duct cells to efflux bicarbonate into the lumen

A
  • They stimulate a chloride channel called CFTR
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22
Q

How does CFTR work

A
  • Forces Cl- into the duct to produce a high enough concentration for the Cl- ions to drive the Chloride bicarb exchanger.
  • Bicarbonate ion then enters the duct in exchange for Cl- ions leaving the duct
23
Q

What type of Cl- channel is CFTR and what happens if it mutated

A
  • cAMP - activated
  • If CFTR is mutated in someone they have Cystic Fibrosis
24
Q

What causes mutated an non functional CFTR in individuals with Cystic Fibrosis

A
  • Mutation in CF gene causes premature degrading of CFTR.
25
Q

What is the effect of non functional CFTR

A
  • Decreased secretion of HCO3- and water
  • Lack of water causes blockage in ducts due to thick secretion of acinar cells
  • Blockages can cause pancreatic tissue destruction (can cause diabetes and maldigestion)
26
Q

What is pancreatic juice

A
  • Mixture of secretions from acinar, duct and goblet cells.
  • Protein - Rich alkaline fluid
27
Q

What is the rate of pancreatic secretion dependant on

A
  • Whether you are fed or fasted
  • Biliary and gastric secretion and intestinal motility
28
Q

What are pancreatic secretion levels like when fasted and fed

A
  • Fasted state - low level of pancreatic release
  • Fed state - Pancreatic release is 5-20 times more than basal levels
29
Q

What other than fat in the duodenal lining stimulates CCK secretion and what happens in the fasted state

A
  • CCK releasing factors (e.g. LCRF)
  • In the fasted state LCRFs are degraded by digestive enzymes to stop CCK production
30
Q

What inhibits pancreatic secretion and how

A
  • Somatostatin inhibits secretin and CCK release
  • Pharmacological inhibitors that imitate somatostatin.
31
Q

What are the phases of pancreatic secretion

A
  • Cephalic phase - 25%
  • Gastric phase - 10%-20%
  • Intestinal phase - 50%-80%
32
Q

What stimulates the cephalic phase of pancreatic secretion and what mediates it

A
  • Sight of food
  • Smell of food
  • Taste of food
  • Medicated by stimulation of Ach receptors on acinar (and duct) cells
33
Q

What stimulates the gastric phase of pancreatic secretion

A
  • Release of gastrin from antral G-cells which signals through CCK receptors on acinar cells.
  • Gastric distension stimulates low levels of pancreatic secretion, through vagovagal gastropancreaytic reflex
34
Q

What stimulates pancreatic secretion in the intestinal phase

A
  • Chyme entering the proximal small intestine stimulates secretion via 3 mechanisms:
    > S cells
    > I cells
    > Reflexes
35
Q

How does stimulation of duodenal S cell by gastric acid stimulate pancreatic stimulation in the intestinal phase

A
  • Duodenal S cells release secretin which stimulates duct cells to secrete HCO3- and fluid
36
Q

How does stimulation of duodenal I cell by lipids stimulate pancreatic stimulation in the intestinal phase

A
  • Duodenal I cells are stimulated to release CCK which stimulates acinar cells to release digestive enzymes
37
Q

How do lipids stimulate pancreatic stimulation in the intestinal phase

A
  • lipids activate vagovagal enteropancreatic reflex that predominantly stimulates acinar cells via M3 receptor
38
Q

How does the pancreas avoid autodigestion

A
  • Producing zymogens (inactive) enzymes
  • Zymogens only activate in the small bowel
  • Acinar cells package zymogens in granules
39
Q

How does the pancreas ensure that zymogens are only activated in the small bowel

A
  • They are only activated when they come into contact with trypsin
  • Trypsinogen only becomes typsin when it comes into contact with enterokinase (Small bowel brush border enzyme only found in small bowel)
40
Q

Describe some specialised features of the granules that acinar cells pack zymogens into

A
  • Low pH - even if zymogens do become active enzymes, they will be non functional
  • Impermeable to proteins - enzymes cannot enter the granule to activate zymogens
  • Enzyme inhibitors are packed into the granules - stop enzymes from activating zymogens
41
Q

What is autodigestion of the pancreas known as

A

Pancreatitis

42
Q

What is the pneumonic to remember the causes of acute pancreatitis (which are for main causes, which are for rare causes)

A
  • GET (main) SMASHED (rare)
  • Gall stones
  • Ethanol
  • Trauma
  • Steroids
  • Mumps
  • Autoimmune
  • Scorpion’s sting
  • Hypercalcaemia, Hypertriglyceridemia, hypothermia
  • ERCP
  • Drugs
43
Q

How is acute pancreatitis diagnosed

A
  • Two of the following 3 features are required
    > Abdominal pain (usually epigastric region that radiates to the back)
    > Serum amylase or lipase > 3
    > Findings of acute pancreatitis on a CT scan
44
Q

What happens in phase 1 of acute pancreatitis

A
  • Premature activation of trypsin
45
Q

What happens in phase 2 of acute pancreatitis

A
  • Intra-pancreatic inflammation caused by digestive enzymes activated by trypsin
46
Q

What happens in phase 3 of acute pancreatitis

A

-Extra-pancreatic inflammation caused by digestive enzymes leaking out of the pancreas

47
Q

What happens in phase 3 of acute pancreatitis

A

-Extra-pancreatic inflammation caused by digestive enzymes leaking out of the pancreas.
- Can lead to sepsis and multiple organ failure

48
Q

How is acute pancreatitis treated (mild)

A
  • Pancreas is rested - IV fluids for dehydration
  • Hourly fluid balance - catheter due to severe hypovolemia
  • Pain relief
48
Q

How is acute pancreatitis treated (mild)

A
  • Pancreas is rested - IV fluids for dehydration
  • Hourly fluid balance - catheter due to severe hypovolemia
  • Pain relief
49
Q

How is acute pancreatitis treated (severe)

A
  • Intensive care
  • Multi-organ support
50
Q

What are some investigations that can be done to work out the cause of the acute pancreatitis

A
  • Ultrasound (gallstones)
  • History (Alcohol)
  • CT
  • ERCP (can also be treatment)
51
Q

What is chronic pancreatitis

A
  • Inflammation of the pancreas that does not heal but gets worse and leads to permanent damage
52
Q

What is the most common cause of chronic pancreatitis and what are some other causes

A
  • Main cause: Chronic alcohol abuse
  • Other causes:
    > Hereditary disorders of the pancreas
    > Cystic fibrosis
    > Hypercalcaemia
    > Hyperlipidaemia
53
Q

How is chronic pancreatitis treated

A
  • Hospitalisation is often required for pain, dehydration and malnutrition
  • Synthetic pancreatic enzyme supplements - when returning to normal diet if pancreas does not secrete enough
  • ERCP to identify and treat complications
  • Diagnostic imaging to identify calcification of pancreas
  • Diabetes monitoring and treatment if required

Digestive System (7 decks)

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