DSA and lecture Bile secretion and Gall bladder function

Question 1

what are the two main functions of bile

Answer 1

play important role in fat digestion and absorption

• help emulsify the large fat particles of the food into many minute particles and the surface of which can then be attacked by lipase enzymes secreted in pancreatic juice
• aid in absorption of digested fat end products through intestinal mucosal membrane

serves as a means for excretion of several waste products including bilirubin and excess of cholesterol

Question 2

what is the composition of the first stage of bile and what secretes it

Answer 2

secreted by the principal cells of the liver (hepatocyes)

contains large amounts of bile acids
cholesterol
other organic constituents

Question 3

what is the composition of the second portion of liver secretion that is added to the initial bile

and what secretes it

Answer 3

This additional secretion is a watery solution of sodium and bicarbonate ions secreted by secretory epithelial cells that line the ductules and ducts.

Question 4

when does the gallbladder begin to empty

what does effective emptying require

Answer 4

When food begins to be digested in the upper gastrointestinal tract, the gallbladder begins to empty, especially when fatty foods reach the duodenum about 30 minutes after a meal.

The mechanism of gallbladder emptying is rhythmical contractions of the wall of the gallbladder, but effective emptying also requires simultaneous relaxation of the sphincter of Oddi, which guards the exit of the common bile duct into the duodenum.

Question 5

what is the most potent stimulus for causing the gallbladder to contract

what is the stimulus for the release of this potent stimulus

Answer 5

By far the most potent stimulus for causing the gallbladder contractions is the hormone cholecystokinin.

This is the same cholecystokinin discussed earlier that causes increased secretion of digestive enzymes by the acinar cells of the pancreas.

The stimulus for cholecystokinin entry into the blood from the duodenal mucosa is mainly the presence of fatty foods in the duodenum.

Question 6

in addition to CCK, what else stimulates the gallbladder

Answer 6

Acetylcholine-secreting nerve fibers from both the vagi and the intestinal enteric nervous system

Question 7

what happens when there is not alot of fat in food we eat

Answer 7

the gallbladder empties poorly

but when there is alot of fat the gallbladder normally empties completely in about 1 hour

Question 8

what are the two sources that liver receives blood from and what do each of these sources provide?

Answer 8

Hepatic artery (25%): Arterial blood which provides the liver’s O2 supply and metabolites for hepatic processing

Hepatic portal vein (75%): venous blood draining the stomach, digestive tract, pancreas, and spleen for processing and storage of newly absorbed nutrients

Question 9

through what does blood leave the liver

Answer 9

hepatic vein

Question 10

what is bile

Answer 10

bitter, neutral or slightly alkaline fluid synthesized by the liver

consists of salts, proteins, cholesterol, hormones, enzymes and bilirubin

Question 11

what is bilirubin

Answer 11

breakdown product of hemoglobin

excreted by the liver in bile

Question 12

what are the primary bile acids

Answer 12

cholic acid and chenodeoxycholic.

the liver converts cholesterol into these

Question 13

what are the secondary bile acids

Answer 13

deoxycholic acid and lithocholic acid.

action of bacteria in terminal ileum and colon may dehydroxylate bile acids into these secondary acids

Question 14

what is the total bile secretion per day

Answer 14

1000 mL/day

Question 15

how much bile does the gallbladder hold

Answer 15

50 ml/day (concentrated bile)

Question 16

what are the four major components of bile

Answer 16

bile salts (cholates, chenodeoxycholate, deoxycholate)

cholesterol and phospholipids

bilirubin

protein and miscellaneous components (Bicarb)

Question 17

what is cholestasis

Answer 17

suppression of bile secretion

Question 18

what are the three major groups of negative effects that occur due to cholestasis

Answer 18

1. regurgitation of bile components (bile acids, bilirubin) into the systemic circulation
   gives rise to the symptoms of jaundice and pruritus (itching).
   
   2. cholestasis damages hepatocytes, as evidenced by the release of liver enzymes (e.g.
      alkaline phosphatase) into the plasma.
   3. because the bile acids do not arrive in the duodenum, lipid digestion and absorption
      may be impaired.