Bile, gall bladder and gall stones Flashcards

1
Q

What forms of the hepatopancreatic duct?

A

Formed out of the union of pancreatic duct and common bile duct; near the duodenal papillla

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2
Q

What is the function of the gallbladder?

Why is the bile concentrated?

A
  • Storage and concentration of bile

* Concentrated because of active Na+ transport (and H2O) from gallbladder

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3
Q

What is the percentage of solids in the hepatic duct bile and gallbladder

What is the pH in the hepatic duct bile and gallbladder

A

2-4 and 10-12

7.8-8.6 and 7.0-7.4

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4
Q

Why does the Ph of bile drop?

A

The pH of bile drops (becomes “acidic”) as Na+ is exchanged for H+

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5
Q

What are the contents of the pancreatic juice?

A

Pancreatic juice: bile salts, bile pigments and dissolved substances in alkaline electrolytes

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6
Q

How large are the bile ductules?

Can water be added via specific tight junctions within ductules?

What do the ductules scavenge?

What do the ductules secrete?

A

Bile → larger ductules and ducts (composition is modified)

Water is (may be) added via specific tight junctions within ductules (cholangiocytes)

The ductules scavenge glucose, amino acids; GSH is hydrolyzed

Ductules secrete IgA (mucosal protection), HCO3- and H2O in response to secretin in the postprandial period

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7
Q

Where does bile flow to and from?

A
Bile flows as follows:
Hepatocytes
       ↓
Bile canaliculi (merge to form ductules)
        ↓
Terminal bile ducts
       ↓
Hepatic ducts (left and right)
       ↓
Common bile duct
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8
Q

What cells are bile secreted from?

A
  1. Hepatocytes: cholesterol, lecithin, bile acids, bile pigments (bilirubin, biliverdin, urobilin, etc.)
  2. Epithelial cells of bile ducts: bicarbonate-rich salt solution
    3. Secretin influences the secretion of bicarbonate-rich salt solutions and H2O
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9
Q

What does increased concentration of bile salt in the blood lead to?

A

• Increased [bile salt]blood → ↑ bile salt secretion into bile canaliculi
Increased secretion →↑flow of bile

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10
Q

When does the sphincter of Oddi contract and relax

A
  • Sphincter of Oddi contracts during periods of fasting

* Sphincter of Oddi relaxes during and after meals

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11
Q

What substances are secreted across the bile canalicular membrane?

A

• Bile acids
• Phosphatidylcholine
• Conjugated bilirubin
• Cholesterol
• Xenobiotics (foreign chemicals/substances, e.g. drugs)
Specific transporters ferry the above into bile
Substances such as water, glucose, Ca2+, GSH, amino acids and urea enter the bile by diffusion

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12
Q

Describe the composition of hepatic and gallbladder bile

A

• Hepatic bile = 97% water; cholesterol, lecithin, bile acids, bile pigments, etc.
• Gallbladder bile: 89% water; HCO3-, Cl-, Ca2+, Mg2+, Na+, cholesterol, bilirubin, bile salts, etc.
Bile concentrated in gallbladder (NaCl and H2O loss → increased solid content)
Bile goes to the gallbladder between meals when sphincter of Oddi is closed

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13
Q

What is the purpose of the conjugation of bile acids (remember when we did the liver lecture - the part where bile is made…)

A

Conjugation helps to increase the ability of bile acids to be secreted and also decreases their cytotoxicity

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14
Q

What are the 4 major types of bile acids found in humans ( we already have leant about 2 - remember in the production of bile in the liver lecture)

A
  • *Cholic acid: 50% = quantitatively more important
  • *Chenodeoxycholic acid: 30%
  • $Deoxycholic acid: 15%
  • $Lithocholic acid: 5%

on image

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15
Q

Why do we produce bile acids: the function of bile acids as metabolic regulators

A
  1. Elimination of cholesterol to bile acids (5% excreted in faeces)
    a. Synthesis and subsequent excretion of bile acids in the faeces represents a significant mechanism for the elimination of excess cholesterol
  2. Reduce the precipitation of cholesterol in gallbladder; bile acids and phospholipids help solubilise cholesterol in the bile
  3. Facilitate the absorption of fat-soluble vitamins (ADEK)
  4. Regulate their own transport and metabolism via enterohepatic circulation
  5. Facilitate the digestion of triglycerides - work in concert with phospholipids (licithin) and monoglycerides to ensure the emulsification of fats
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16
Q

Describe the mechanisms controlling the secretion of bile into the duodenum

A

on image

Motilin → gallbladder motility and ↑ volume of gall bladder secretions

17
Q

What controls the contraction of the gallbladder and the release of bile into the duodenum?

A

Presence of fatty meal stimulates secretion of cholecystokinin (CCK):

on image

18
Q

Describe the release of bile into the duodenum

A

On image

19
Q

Most bile salts are reabsorbed.

What are they reabsorbed by?

A

Na+-bile salt coupled transporters

The recycling pathway from intestine to liver and back to intestine = enterohepatic circulation – recycling of bile salts

20
Q

What will interruption of enterohepatic circulation (e.g. after ileal resection) cause?

A

Excess synthesis of bile salts by the liver

Kidneys will excrete the synthesised bile salts (and some cholesterol)

21
Q

What are gallstones made of?

A

Bile salts (= bile compounded with a cation, e.g. Na+), cholesterol and phospholipids

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

22
Q

What causes increased cholesterol?

How do those 3 ingredients form gallstones?

A

Liver secretes excess

Reabsorption of salt and water

The cholesterol crystallises and forms gallstones
precipitation of bile pigments

23
Q

What are the two types of gall stones and what are they caused by?

A
  • Cholesterol stones (85%): obesity; ↓ bile acids; ↓ phospholipids
  • Calcium bilirubinate stones – due to ↑ conjugated bilirubin (haemolytic anaemia)
24
Q

Describe the factors involved with gallstone formation (Bile stasis, malabsorption, chronic infection, ss, nf and glycol)

A
  1. Bile stasis: stones form in bile that is sequestered in the gallbladder rather than bile that is flowing in the bile ducts into the duodenum
  2. Decreased amount of bile acids due to malabsorption (in cystic fibrosis – dehydrated and acidic; 10% higher incidence; Crohn’s disease); problems with bile production – gallbladder and cystic ducts can be blocked by thick mucus
  3. Chronic infection – bacteria help in the formation of pigment stones
  4. Super-saturation of bile with cholesterol
  5. Presence of nucleation factors or glycoprotein??
25
Q

Where can a gallstone lodge and what can it cause?

Why is bile yellow?

What colours faeces?

A

• Small gallstones easy passage via bile duct
• Larger gallstones lodge in the opening of gallbladder (right upper quadrant pain; jaundice)
• Duct from pancreas joins the bile duct before it joins the duodenum
• Lodging of gallstones at this point causes the stoppage of bile and pancreatic secretions (pressure builds up; right upper quadrant pain; jaundice)
Consequence → nutritional deficiency as digestion of fats is inefficient
• Further pressure build up causes decreased secretion of bile and right upper quadrant pain Jaundice (increased accumulation of bilirubin in blood)
• Bile is yellow because of bilirubin
• … colour of urine
• Stercobilin colours faeces

26
Q

How can we diagnose the gallstones: visualising the gallbladder

A

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

Cholescintigraphy: administer tecnetium-99m-labelled derivative of iminodiacetic acid (radioactive tracer)
→ acquire images of gall bladder and ducts

Endoscope retrograde cholangiopancreotography (ERCP): inject contrast media from an endoscope channel and visualise the biliary tree

What else could you do?

Insert device(s) and remove gallstone fragments that may be obstructing the bile flow, pancreatic juice or both

27
Q

Describe the clinical features of a gallstone

A
  • 85% of cases are asymptomatic (gallstones remain in gallbladder)
  • If the neck of the cystic duct is impaired → biliary pain of right upper quadrant ensues (acute cholecystitis)
  • Gallstones that impact common bile duct → obstruction of bile flow and cholestatic jaundice which can cause bacterial infections (cholangitis) and right upper quadrant pain
  • Gallbladder will secrete mucus if inflamed and rupture (mucocele or hydrops)