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SGUL - Physiology 1 > Bile, Gall Bladder and Gall Stones > Flashcards

Bile, Gall Bladder and Gall Stones Flashcards

1
Q

What is the ampulla of Vater formed from?

A

Union of the pancreatic duct and the common bile duct.

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2
Q

Where is the ampulla of Vater found?

A

Duodenal papilla

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3
Q

What is the general function of the gallbladder?

A

Stores and concentrates bile.

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4
Q

Why does bile become concentrated within the gall bladder?

A

Active Na+ transport from the gallbladder.

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5
Q

Why does bile become acidic within the gall bladder?

A

Na+ is exchanged for H+

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6
Q

Describe bile acid synthesis.

A
  • Occurs in liver cells
  • Synthesise primary bile acids (cholic acid and chenodeoxycholic acid) via cytochrome P450-mediated oxidation
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7
Q

Describe the pathway of bile flow

A

Hepatocytes
⬇
Bile Canaliculi
⬇
Terminal Bile ducts
⬇
Hepatic ducts (left and right)
⬇
Common Bile duct

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8
Q

What two components make up a bile acid?

A
  • bile
  • a cation (eg. Na+)
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9
Q

What two cells secrete bile salts?

A

HEPATOCYTES: secrete cholesterol, bile acids, bile pigments (bilirubin, biliverdin, urobilin)
EPITHELIAL CELLS OF BILE DUCTS: secrete bicarbonate-rich salt solution

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10
Q

What does secretin influence?

A

Secretion of bicarbonate-rich salt solutions

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11
Q

Can cholecystomised patients have a good quality of life?

A

Yes, as long as they don’t eat too much fatty food.

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12
Q

What substances are secreted across the canalicular membrane via transporter proteins?

A
  • bile acids
  • conjugated bilirubin
  • cholesterol
  • xenobiotics (foreign chemical/ substance, e.g. drugs)
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13
Q

What substances are secreted into bile by diffusion?

A
  • Water
  • Glucose
  • GSH (glutathione)
  • Amino acids
  • Urea
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14
Q

Describe the composition of hepatic bile.

A

97% water; cholesterol, lecithin, bile acids, bile pigments

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15
Q

Describe the composition of gallbladder bile

A

89% water; Cl-, Ca2+, Na+, cholesterol, bilirubin, bile salts

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16
Q

When does bile go into the gallbladder between meals?

A

When Sphincter of Oddi is closed

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17
Q

Describe bile acids.

A
  • Made from cholesterol
  • Secreted into bile
  • Conjugated to glycine or taurine.
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18
Q

What is the purpose of bile conjugation?

A
  • Increase the ability of bile acids to be secreted
  • Decrease cytotoxicity
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19
Q

List and describe the 4 major bile acids found in humans.

A

PRIMARY BILE ACIDS:
- Cholic Acid
- Chenodeoxycholic Acid
SECONDARY BILE ACIDS:
- Deoxycholic Acid: 15%
- Lithocholic Acid: 5%

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20
Q

What are the differences between primary and secondary bile acids?

A
  • Primary bile acids formed in liver
  • Secondary bile acids formed in colon
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21
Q

Outline cholesterol conversion to secondary bile acids.

A

Cholesterol converted to primary bile acids, then to secondary bile acids.

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22
Q

List the main functions of bile/bile acids as metabolic regulators. PART 1

A
  • elimination of excess cholesterol to bile acids (5% excreted in faeces)
  • reduce precipitation of cholesterol in gallbladder (bile acids and phospholipids solubilise cholesterol in bile)
  • facilitate the absorption of fat-soluble vitamins (ADEK)
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23
Q

List the main functions of bile/bile acids as metabolic regulators. PART 2

A
  • regulate their own transport and metabolism via enterohepatic circulation
    -facilitate the digestion of triglycerides (work in cohort with phospholipids (lecithin) and monoglycerides to ensure the emulsification of fats)
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24
Q

List the main functions of bile/bile acids as metabolic regulators. PART 3

A
  • Act as emulsifying agents that render fats accessible to pancreatic lipase]
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25
Q

Describe the contraction of the gallbladder during the intestinal phase. PART 1

A
  • Vagus nerve conveys information about the state of the body’s organs to the CNS
  • Conveys contents of duodenum to the CNS.
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26
Q

Describe the contraction of the gallbladder during the intestinal phase. PART 2

A
  • If duodenum contains lipids, causes the release of CCK
  • Stimulates the release of bile which helps in the emulsification of fats and prepares them for digestion by pancreatic lipases.
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27
Q

What is CCK released in response to?

A

Lipids/fats

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28
Q

What is secretin released in response to?

A

HCl in the duodenum.

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29
Q

What occurs due to secretin release?

A

Stimulate duct cells in the liver (to release a bicarbonate-rich solution)

30
Q

Describe the mechanisms controlling the secretion of bile into the duodenum. PART 1

A
  • When lipids are sensed in the duodenum, trigger the release of CCK
  • Directly, contracts the gallbladder.
31
Q

Describe the mechanisms controlling the secretion of bile into the duodenum. PART 2

A
  • Indirectly, sends a signal to the dorsal vagal complex, which then sends a signal back down to contract the gallbladder (via ACh) and relax the Sphincter of Oddi (via NO/VIP).
32
Q

What can also control bile secretion?

A
  • Motilin - induces gallbladder emptying
  • Antral contractions
33
Q

What are all of the mechanisms controlling bile secretion, mediated by?

A
  • Distention
  • Neuronal and hormonal signals.
34
Q

On a molecular level, explain how CCK induces bile secretion into the duodenum. PART 1

A
  • Chyme enters the duodenum causing the release of CCK and secretin from the duodenal enteroendocrine cells.
  • CCK and secretin enter the bloodstream, absorbed by the intestinal mucosa.
35
Q

On a molecular level, explain how CCK induces bile secretion into the duodenum. PART 2

A
  • CCK induces the secretion of enzyme-rich pancreatic juice.
  • Secretin causes the secretion of bicarbonate-rich pancreatic juice.
36
Q

On a molecular level, explain how CCK induces bile secretion into the duodenum. PART 3

A
  • Bile salts and secretin are transported via the bloodstream and stimulates the liver to produce bile more rapidly.
  • CCK causes the gallbladder to contract and the hepatopancreatic sphincter to relax; bile enters the duodenum.
37
Q

On a molecular level, explain how CCK induces bile secretion into the duodenum. PART 4

A
  • During the cephalic and gastric phases, vagal nerve stimulation causes weak contractions of the gallbladder.
38
Q

Describe how bile salts are ‘recycled’. PART 1

A
  • Reabsorbed by Na+-bile salt coupled transporters.
  • Returned to the liver and secreted again into the bile.
39
Q

Describe how bile salts are ‘recycled’. PART 2

A
  • Recycling pathway from the intestine to the liver and back to the intestine is the enterohepatic circulation (via the hepatic portal vein).
40
Q

Both primary and secondary bile acids are removed by the intestine into the liver via the portal circulation. Explain how. PART 1

A
  • Specific transporters in the terminal ileum that transport bile salts from the lumen of the digestive tract to the intestinal capillaries.
  • Bile salts are transported directly to the liver via the hepatic portal vein.
41
Q

Both primary and secondary bile acids are removed by the intestine into the liver via the portal circulation. Explain how. PART 2

A
  • Hepatocytes take up bile salts from the blood, and increase the secretion of bile salts into the bile canaliculi
  • Canaliculi are the passageways that convey bile into the larger bile ducts.
42
Q

Both primary and secondary bile acids are removed by the intestine into the liver via the portal circulation. Explain how. PART 3

A

95% of the bile that is released into the small intestine is recycled via the enterohepatic circulation, 5% is lost in the faeces.

43
Q

What will interruption of the enterohepatic circulation cause?

A
  • excess synthesis of bile salts by the liver (compensate for losing bile salts)
  • kidneys will excrete the synthesised bile salts (and some cholesterol)
44
Q

Describe the formation of gallstones.

A

Changes in the composition of bile may cause cholesterol to precipitate out to form gallstones.

45
Q

What causes the increased cholesterol that could cause gallstones?

A
  • excess excretion by liver
  • reabsorption of water and salt provides environment for gallstones to form.
46
Q

What are the two types of gallstones?

A
  • cholesterol stones - due to obesity
  • calcium bilirubinate - due to increased conjugated bilirubin
47
Q

List some factors involved in gallstone formation. PART 1

A
  • Bile Stasis: stones form in bile that is sequestered in the gallbladder rather than flowing in the bile ducts into the duodenum
  • Decreased amount of bile acids due to malabsorption (in cystic fibrosis - dehydrated and acidic; 10% incidence)
48
Q

List some factors involved in gallstone formation. PART 2

A
  • Problems with bile production
  • Chronic infection - bacteria help in the formation of pigment stones
  • Supersaturation of bile with cholesterol
49
Q

How would you visualise the gallbladder in a case of gallstones? PART 1

A

Ultrasonography and computer tomography: explore the upper right quadrant of the gallbladder to detect gallstones

50
Q

How would you visualise the gallbladder in a case of gallstones? PART 2

A

Cholescintigraphy: administer technetium-99m-labelled derivative of iminodiacetic acid (radioactive tracer), to show images of the gallbladder and its ducts (inject CCK to see how the gallbladder behaves)

51
Q

How would you visualise the gallbladder in a case of gallstones? PART 3

A

Endoscope retrograde cholangiopancreatography (ERCP): can visualise the biliary tree by injecting contrast media from an endoscope channel

52
Q

What symptoms will you end up with if a gallstone got stuck in each of the three possible places it could form? PART 1 - The Cystic Bile Duct

A
  • painful gallbladder contractions
  • inflammation of the gallbladder (acute cholecystitis)
53
Q

What symptoms will you end up with if a gallstone got stuck in each of the three possible places it could form? PART 2 - The Common Bile Duct

A
  • pain and nausea
  • lack of bile release
  • failure to excrete bilirubin leads to jaundice
  • can cause bacterial infection (cholangitis)
54
Q

What symptoms will you end up with if a gallstone got stuck in each of the three possible places it could form? PART 3 - The Common Bile Duct

A
  • inappropriate activation of pancreatic enzymes
  • acute pancreatitis
55
Q

What is pancreatic juice made from?

A

→ bile salts
→bile pigments
→dissolved substances in alkaline electrolytes

56
Q

Where is water added to bile?

A

Ductules

57
Q

What do the ductules do?

A

→The ductules scavenge glucose, amino acids and hydrolyse GSH

58
Q

What do ductules secrete and in response to what?

A

→ IgA (mucosal protection)
→HCO3-
→ H2O

59
Q

When is secretion of bile the greatest?

A

→greatest during and after a meal

60
Q

What does increased bile salt concentration in the blood mean?

A

→ increased bile salt secretion into bile canaliculi

61
Q

When does the sphincter of Oddi contract?

A

→ during periods of fasting

62
Q

When does the sphincter of Oddi relax?

A

→ relaxes during and after meals.

63
Q

What acids are formed from the neutral pathway and in what amounts?

A

→cholic acid
→ chenodeoxycholic acid

64
Q

What are the conversions that intestinal bacteria do?

A

→Chenodeoxycholic acid → Lithocholic acid and Ursodeoxycholic acid
→Cholic acid → Deoxycholic acid

65
Q

What activates the cephalic phase?

A

→taste
→ smell

66
Q

What causes the Sphincter of Oddi to relax?

A

→NO and VIP

67
Q

What does a high cholesterol content of bile do?

A

→The higher the cholesterol content of bile the greater the concentrations of phospholipid and bile salts.

68
Q

What causes increased cholesterol in gallstone patients?

A

→Liver secretes excess cholesterol
→Reabsorption of salt and water
→Cholesterol crystallizes and forms gallstones
→Precipitation of bile pigments

69
Q

How do small gallstones pass?

A

→ easy passage via bile duct

70
Q

What does lodging of gallstones cause?

A

→stoppage of bile and pancreatic secretions

SGUL - Physiology 1 (68 decks)

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