SS1. Bile production of hepatocytes

Question 1

Where do hepatocytes secrete hepatic bile into?

Answer 1

bile caniculi

Question 2

What is the pH of bile?

Answer 2

7-8, isotonic, resembles plasma in ionic composition

Question 3

What can be found in bile? (4)

Answer 3

Bile salts (emulsify cells into micelles)
Bile pigments
Lecithin
Mucus

Question 4

What are primary bile acids & where are they formed?

Answer 4

Cholic acid
Chenodeoxycholic acid.
Formed in hepatocytes.

Question 5

What are the (2) secondary bile acids and where are they formed?

Answer 5

Deoxycholic acid
Lithocholic acid
Formed in the intestine by dehydroxylation action of bacteria on primary acids.

Question 6

Which AA do primary bile acids conjugate to and why?

Answer 6

Glycine, taurine, forms water-soluble bile salts. Aggregate & form micelles.

Question 7

What are the two secretory mechanisms involved in the formation of bile in the liver?

Answer 7

1) Bile-acid dependent fraction

2) Bile acid independent fraction.

Question 8

Explain bile-acid dependent fraction

Answer 8

Rate of which bile salts are secreted into canaliculi and are returned to the liver.

Question 9

on which circulation type does bile-acid dependent fraction depend on

Answer 9

The enterohepatic circulation, in which the bile salts are reused.

Question 10

Explain bile acid independent fraction

Answer 10

Secretion of H2O & electrolytes by hepatocytes and ductal epithelial cells.

1) Na2+ actively transported into bile canaliculi
2) passive movement of Cl- ions and H2O.
3) bicarbonates are secreted into bile by ductal cells & are followed by passive movement of sodium and H2O.

Question 11

How much of the bile salts are reabsorbed via the enterohepatic circulation?

Answer 11

95%

Question 12

Explain how the uptake of bile salts with the enterohepatic circulation works (6)

Answer 12

1) Cholesterol e.g. is turned into primary bile acids, into bile salts in liver.
2) Via common hepatic duct into cystic duct, the bile is stored in gall bladder until a meal.
3) Meal: cck makes gallbladder contract. Bile is inserted back into cystic duct into common bile duct
5) via duodenum, the bile moves to ileum.
6) Bile salts/fats are reabsorbed by the liver.

Question 13

What is the role of the gall bladder?

Answer 13

Storing bile that is not immediately required for digestion.

Question 14

How does the gall bladder concentrate bile?

Answer 14

It absorbes sodium, chloride, bicarbonate & H2O

Question 15

What is the mucosa gall bladder?

Answer 15

single layer of epithelial cells, bound by tight junctions. Forms large channels between cells.

Question 16

Explain how the gall bladder takes up sodiu, chloride, bicarbonate and H2O

Answer 16

1) Na+, HCO3- and Cl- are cotransported into channels. Creates regions of high osmotic pressure at the apical regions of channel, creates osmotic gradient.
2) Water follows passively.

Question 17

What is the primary mechanism responsible for concentration of bile?

Answer 17

co-transport of sodium, chloride, bicarbonate across apical membranes & efflux of NA+ mediated by Na pump.

Question 18

What are cholagugues?

Answer 18

substances that increase flow of bile b y stimulating the gall bladder to contract.