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Question 1

What are the charactersictics of chyme?

Answer 1

AcidicHypertonicPartly digested

Question 2

How are each of the characteristics corrected?

Answer 2

Acidity - HCO3- secretion Hypertonicity - H2O movement through duodenal wallPartly digested - enzymes and bile salts

Question 3

Where is the HCO3- for acidity correction secreted from?

Answer 3

PancreasDuodenal mucosaLiver

Question 4

Where do the factors needed for complete digestion come from?

Answer 4

Enzymes from pancreas and duodenal mucosaBile acids from the liver

Question 5

What is bile made up of?

Answer 5

Bile acid dependent componentBile acid independent component

Question 6

Describe the things that make up the bile acid dependent component

Answer 6

Made up of bile salts which are cholic acid and chenodeoxycholic acidCholesterolBile pigments

Question 7

Where is the bile acid dependent component secreted from?

Answer 7

Hepatocytes lining the canaliculi

Question 8

Why are bile salts important?

Answer 8

Have a major role in the digestion and absorption of fat – increase the surface area of fats to be absorbed by incorporating fats into micelles.

Question 9

Describe the components of the bile acid independent components

Answer 9

Secretes HCO3-/alkaline juice like the pancreatic duct cells

Question 10

Where is the bile acid independent component secreted from?

Answer 10

Duct cells lining the intra-hepatic bile ducts

Question 11

What makes up the microscopic structure of the liver?

Answer 11

Hepatic lobules and acinii

Question 12

Describe the hepatic lobule

Answer 12

Made up of a central vein an the surrounding liver tissue. The vein drains blood to the systemic system from the hepatic portal vein and the hepatic arteries via sinusoids.

Question 13

Where is bile formed?

Answer 13

In canaliculi

Question 14

Decribe what happens in response to gastric emptying

Answer 14

Duodenum secretes cholecystokiinin. Stimulate gall bladder contractionConcentrated bile acids, pancreatic enzymes and alkali from liver and pancreas are secreted into the duodenum via the ampulla of vater. They travel to the terminal ileum where they are actively reabsorbed by the epithelium to be brought back tot he liver via the hepatic portal system. Hepatocytes actively take up bile acids and re-secrete them into the canaliculi.

Question 15

What is the main function of the gall bladder?

Answer 15

Stores bile acids

Question 16

What risk is there of storing bile acids?

Answer 16

Risk of precipitation when concentrating the bile acids, which could lead to gall stones. (Remove water to concentrate it)

Question 17

Describe the effects of gall stones

Answer 17

• often asymptomatic- can move into the neck or the biliary tree - causes biliary colic and/or obstruction

Question 18

What are some further complications of gall stones?

Answer 18

Cholecystisisinfection of the gall bladder

Question 19

When can pain from gall stones be worse?

Answer 19

After eating as CCK causes contraction of the gall bladder

Question 20

What is secreted from the duct cells of the exocrine pancreas?

Answer 20

Proteases– trypsin, chymotrypsin, elastase, carboxypeptidaseLipasesAmylases

Question 21

What are the cells that you find in the exocrine pancreas?

Answer 21

Acinar and duct cells

Question 22

What does the exocrine pancreas do?

Answer 22

Acini secrete zymogen granules which contain inactive enzymes via exocytosis. Are activated in the intestine by enzymatic cleavageDuct cells secrete HCO3-/alkaline juice

Question 23

How is HCO3- secreted into the duodenum?

Answer 23

Na gradient is set up by NaKATPase pump, which causes H+ ions to be actively secreted out of the cell. They bind to HCO3-, forming CO2 and H2O which are taken up into the cell. H+ and HCO3- are reformed inside the cellsHCO3- is exported to the duct lumen, to travel to the duodenum which the H+ is recycled and travels out into the ECF to collect more HCO3-

Question 24

What is the secretion of HCO3- stimulated by?

Answer 24

Secretin which is released from jejunal cells due to low pH

Question 25

What stimulate acinar pancreatic secretions?

Answer 25

CCK stimulates which is released from duodenal APUD cells in response to hypertonicity and fats

Question 26

What stimulates ductal pancreatic secretions?

Answer 26

Secretin stimulates which is released from the jejunal cells in response to a low pH.

Question 27

What is biliary secretion stimulated by?

Answer 27

CCK from the duodenum in response to gastric emptying. This stimulates gall bladder contraction.

Question 28

Describe enterohepatic circulation

Answer 28

Bile acids are secreted by gall bladder with alkaline secretions which travel down tot eh duodenum via the ampulla of vater. They then travel through th duodenum to the terminal ileum where they are actively reabsorbed by the epithelium there. The bile acids are then transported to the hepatocytes via the hepatic portal system.

Question 29

What is the consequence of inadequate bile/pancreatic lipase secretion?

Answer 29

Inadequate fat digestion and reabsorption causing steatorrhoea.

Question 30

Describe the mechanism of digestion of fats

Answer 30

Bile acids break fats down into micelles giving a high surface area for the action of lipases which cleave fatty acids from glycerol. THe micelles carry the FAs and glycerol into the “unstirred layer” where FAs can diffuse into the epithelial cells. Once the FAs and glycerol are in the epithelial cells, they are converted into TAGs and re-expelled as chylomicrons into the blood.

Question 31

Describe steatorrhoea

Answer 31

When inadequate amount of biles acids or pancreastic enzymes are secreted so fat appears in the faeces. – Are pale, float and are foul smelling

Question 32

What is the mechanism of jaundice?

Answer 32

An accumulation of bilirubin in in the blood, if it cannot be excreted

Question 33

What is bilirubin?

Answer 33

A bile pigment which is an excretory product. It if conjugated in the liver and secreted in the bile to be excreted in faeces.