Exam 3 (Lecture 10) - Secretory Activities of the Liver

Question 1

What cells in the liver make/secrete bile into the canaliculi? What is the pathway of bile flow?

Answer 1

Hepatocytes

Bile acids secreted from hepatocytes > canaliculi > hepatic bile duct from each liver lobe > bile duct > cystic duct > gall bladder

Question 2

Is bile duct epithelium metabolically active and capable of altering the composition of canalicular bile? What is added? How do bile duct epithelial cells function in a manner similar to the centroacinar and duct cells of the pancreas?

Answer 2

1) Yes

2) Water and electrolytes (mostly HCO3-)

3) Respond to secretin by increasing HCO3- secretion

Question 3

Describe how bile acids are able to emulsify dietary lipids and solubilize the products of fat digestion.

Answer 3

Bile acids are detergents
- Dual solubility (hydrophobic-hydrophilic lipid soluble combination); allows lipid to be soluble in water
- Emulsifies (increases surface area) of dietary lipids
- Digestion and absorption of fats

Question 4

What are the major functional components of bile?

Answer 4

1) Phospholipids
2) Cholesterol
3) Bile acids
4) Bile pigments

Question 5

Name the two bile pigments. How are bile pigments made? Where is bilirubin incorporated in the liver? Bilirubin is eventually converted to stercobilin and urobilinogen in the large intestine by bacteria. Stercobilin gives the characteristic color to __________ and urobilin gives the characteristic color to ____________. What happens to bilirubin if the liver is not functioning properly?

Answer 5

1) Biliverdin and bilirubin

2) Made from the breakdown of the heme molecule of RBCs

3) Bilirubin is incorporated into bile

4) Feces

5) Urine

6) If the liver is not functioning properly, bilirubin builds up in tissues = icterus (jaundice)

Question 6

Describe how the gall bladder is able to store and concentrate bile. What are the functions of CCK and secretin?

Answer 6

The simple columnar epithelium concentrates bile by absorbing Na+, Cl-, HCO3-, and H2O from the bile.

CCK:
- When fat reaches the duodenum, the GI endocrine cells are stimulated to secrete CCK
- Strong contraction of the gallbladder
- Relaxation of the hepatopancreatic sphincter
- Stored bile is released into the duodenum

Secretin:
- Stimulates H2O and HCO3- secretion from the hepatic bile ducts
- Increases duodenal pH

Question 7

Describe enterohepatic circulation and why this type of circulation is important.

Answer 7

Small intestine (ileum) > hepatic portal vein > liver > small intestine > bile acids reach the caudal VC (systemic circulation) and are found in very low concentrations.

This is important because if the bile acids are found in too high of concentration, there will be a metabolic acidosis problem.

Question 8

How can a problem with the pancreas cause a problem in the liver?

Answer 8

Because of their close anatomical proximity:
- If the pancreas is inflamed, the inflammation can travel up the common bile duct, get into the
intrahepatic bile ducts and back up into the canaliculi and then into the hepatocytes

  - This causes an increase in the release of ALP into venous blood