Bile Secretion Flashcards

1
Q

What is bile required for?

A

Digestion and absorption of many fats and fat-soluble vitamins

Excretion of water-insoluble substances such as cholesterol and bilirubin

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2
Q

What are primary and secondary bile acids?

A

Primary - synthesized in liver from cholesterol

Secondary - converted fraction of primary acids by bacteria

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3
Q

What are bile salts?

A

Bile acids conjugated with glycine/taurine and Na ions

More water soluble at intestinal pH

Ionized at physiologic pH and not passively absorbed

Amphipathic, so emulse fats

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4
Q

What phospholipids are present in bile?

A

Lecithins, solubilized by bile salt micelles

Makes solubility of other lipids more effective

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5
Q

What happens if there is more cholesterol in bile that can be solubilized?

A

Crystals form in bile, may serve as seed for gallstone formation

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6
Q

What is bilirubin?

A

Principal pigment in bile

Insoluble until conjugated with glucuronic acid in liver

Secreted from liver as soluble salt bilirubin glucuronide

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7
Q

What is jaundice?

A

Yellowish tint of body tissues

Due to large quantities of bilirubin in plasma

Caused by increased hemolysis, obstruction of bile duct, or damage to liver

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8
Q

What is the apical sodium-dependent bile salt transporter?

A

ASBT is responsible for absorbing most bile salts in the terminal ileum

Bile acids bind to ileal bile acid binding protein in enterocyte

Enter portal blood via organic solute transporter (OST)

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9
Q

What is sodium-taurocholate cotransporting peptide (NTCP)?

A

Hepatocytes use it to extract bile salts along with Na from the portal blood

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10
Q

How do bile acids get transported back into the bile duct?

A

Via ATPase-dependent bile salt export pump (BSEP) and some via MRP2

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11
Q

What can result from defects in BSEP?

A

Cholestasis - reduction in or lack of bile flow

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12
Q

What occurs to bile salts not reabsorbed in small intestine?

A

Excreted in feces, rate of bile salt synthesis determined by rate of return to liver

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13
Q

What is the bile-independent fraction of biliary secretion?

A

Refers to volume of secretion of water and electrolytes

Secretin stimulates secretion of HCO3 and water

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14
Q

What is the bile-dependent fraction of biliary secretion?

A

Refers to quantity of bile salts secreted by liver

Related to amount reabsorbed by the liver

Bile salts and bile Acids inhiit new vile acid synthesis

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15
Q

What are choleretics?

A

Potent stimulators of bile secretion

Bile salts and acids act at choleretics

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16
Q

What are the functions of the gallbladder?

A

Storage - collects and concentrates bile by removing Na, Cl, and HCO3

Contraction - stimulated by CCK (acts directly on smooth muscle, and vagus/intrinsic nerves)

CCK also relaxes the sphincter of oddi

17
Q

What are the two types of gallstones?

A

Cholesterol and Pigment stones

18
Q

What are cholesterol gallstones?

A

Most gallstones in western society

Cholesterol crystallized because of supersaturation, act as nucleus for stone formation

19
Q

What are pigment gallstones?

A

Composed of calcium bilirubinate

Bilirubin becomes unconjugated, which is now insoluble in bile

Precipitates with Ca to begin stone-forming process

20
Q

What is a cholecystectomy?

A

Surgical removal of gallbladder

Normal digestion unaffected, bile empties slowly, but continuously from liver

Fats can be digested, but high fat food should be avoided