Bile

Question 1

Purpose of Bile

Answer 1

-Bile helps rid body of some toxins and extra cholesterol
-Lipids are hydrophobic and are unable to get through unstirred water layer in the small intestine; leading to little absorption
 Unstirred water layer is a result of laminar flow AND thick mucus layer protecting enterocytes that also slows the flow down
 Bile works with lipids to form a micelle that aids in carrying lipids through the unstirred water layer so they can be absorbed by enterocytes in the small intestine
 Lipids are lipohilic and therefore do not require transporters to enter the membrane

Question 2

Bile Formation

Answer 2

o Cholesterol backbone – therefore need cholesterol form diet and synthesis to make bile
o Glycocholic acid – hydrophobic/lipophilic
 Conjugated to glycine or taurine which makes it amphipathic (hydrophilic/lipophilic) (primary bile acids)
• Because they are amphipathic, they are able to get through unstirred water layer
o Secreted into bile canaliculi of liver and then to bile duct
o Bile is an osmotic agent and so it will draw water (and electrolytes) in; when secreted, it will contain bile and buffer (water + electrolytes)

Question 3

Micelle Formation

Answer 3

Fat droplet  add bile salts and emulsion occurs forming smaller lipid droplets  bile salts + pancreatic lipase + co-lipase causes micelle formation
o Pancreatic lipase – hydrolyzes lipids;
o Co-lipase (secreted by pancreas) – “superhero” that binds with bile and opens door so pancreatic lipase can access lipids

Question 4

Duodenum

Answer 4

emulsifies fats – acts like detergent and breaks lipid into tiny little particles so it can be digested

Question 5

Jejunum

Answer 5

micelle formation and fat absorption

Question 6

Ileum

Answer 6

– active absorption of bile acids; lose ~10% of bile with each cycle and thus also some cholesterol, bilirubin, and random waste products

Question 7

Bile Recycling

Answer 7

enterohepatic circulation)– occurs primarily in the ileum; liver will replace the lost bile and re-secrete the bile; continues to be recycled until chyme stops coming out of stomach and signals are shut down
 Secondary acids – bacteria in the intestines will dehydroxylate the primary bile salts

Question 8

Bilirubin

Answer 8

– major end product of hemoglobin degradation and can be used to diagnose hemolytic blood and liver diseases; responsible for the color of bile

Question 9

Gallstones

Answer 9

o Caused by accretion of components of bile
o Can block ducts and lead to emergency surgery
o Treatment: surgically remove (cholecystectomy)

Question 10

Cholecystectomy (outcomes & effect)

Answer 10

• performed in response to cholecystitis (inflammation with or without gall stones)
  o 5-40% postop patients may experience chronic GI distress and pain in upper right abdomen
  o Up to 20% post op patients can develop diarrhea that takes years to resolve
   More Bile initially being secreted; creates solvent drag because it is an osmotic agent that will draw water and salts towards it (into the intestines); with extra salts in intestines less water will be able to be absorbed
  o Effects: liver will keep producing bile during digestion; will produce more than normal because there is no storage
   When the Sphincter of Oddi closes (when chyme is out of duodenum) the recycled bile stays in the bile duct

Question 11

Ileum Removal

Answer 11

• Lose the bile transporters in the terminal ileum so there is little, if any, recycling
• Bile secreted by the gall bladder and liver will be excreted
• Overall: liver must secrete more bile since there is no recycling
   Increase in bile excretion reduces the ability of colon to absorb sodium and water and will cause diarrhea
  • Cholestyramine – sequesters and binds bile in an insoluble complex that reduces the osmotic effects, thus reducing diarrhea