Lecture 10-Pancreas and Liver

Question 1

What are the properties of chyme once it leaves the stomach?

Answer 1

• low pH
• hypertonic
• partially digested

Question 2

Why is chyme hypertonic as it leaves the stomach?

Answer 2

Stomach is impermeable to water so chyme couldn’t be diluted

Question 3

How does the duodenum make chyme isotonic?

Answer 3

Duodenum is permeable to water so the hypertonic chyme draws water in from ECF

Question 4

How is the low pH of chyme counteracted in the duodenum?

Answer 4

Duodenum secretes secretin which acts on the pancreas to release HCO3- which neutralises the acidic chyme

Question 5

How is the chyme further digested in the duodenum?

Answer 5

Duodenum secretes CCK which acts on the pancreas to release enzymes and on the gallbladder to contract and release bile by relaxing the sphincter of Oddi

Question 6

What stimulates pancreatic secretions?

Answer 6

Secretin, CCK and autonomics

Question 7

What type of cell produces pancreatic enzymes?

Answer 7

Acini cells

Question 8

Which enzymes released by the pancreas are activated and which are inactivated and why?

Answer 8

• amylase and lipase are activated

- proteases are inactivated as they are stored in zymogen granules

Question 9

Give examples of inactive proteases

Answer 9

• trypsin
• chymotrypsin
• elastase
• carboxypeptidase

Question 10

How do pancreatic secretions reach the duodenum?

Answer 10

Pancreatic duct and ampulla of Vater (=hepatopancreatic duct)

Question 11

What does the liver secrete into the duodenum in response to chyme?

Answer 11

Bile

Question 12

What is bile made up of?

Answer 12

Bile acids and bile pigments and alkaline solution

Question 13

Blood from the whole gut reaches the liver through which vessel?

Answer 13

Portal vein

Question 14

What are the structural units of the liver hepatocytes?

Answer 14

Hexagonal lobules

Question 15

Describe the triad of structures at each corner of a lobule

Answer 15

Portal vein, hepatic artery and bile duct

Question 16

Which vessel is in the centre of the liver lobule

Answer 16

Central vein

Question 17

How does blood enter the liver lobule?

Answer 17

Through hepatic artery and portal vein into central vein via sinusoids

Question 18

How does bile flow out of the liver lobule?

Answer 18

Along canaliculi, bile duct and into duodenum

Question 19

What is the functional area of a lobule called?

Answer 19

Acinus

Question 20

What do the zones of the lobule correspond to?

Answer 20

Distance from arterial blood supply

Question 21

True or false: bile is produced continuously by the hepatocytes and duct cells

Answer 21

TRUE

Question 22

How is bile stored in the gallbladder?

Answer 22

Concentrated form by removing water and ions

Question 23

What is the function of bile?

Answer 23

To emulsify fats

Question 24

What secretes bile acids and pigments and where?

Answer 24

Hepatocytes into canaliculi

Question 25

What secretes alkaline juices of bile and what stimulates this release?

Answer 25

Bile duct cells and stimulated by secretin

Question 26

What are bile salts?

Answer 26

Bile acids conjugated with AA

Question 27

What are the two primary bile acids?

Answer 27

Cholic acid and chenodeoxycolic acid

Question 28

Why are bile acids conjugated?

Answer 28

• bile acids are not always soluble at duodenal pH
• bile salts are amphipathic
• bile salts allow emulsification of dietary lipids

Question 29

Describe how bile salts aid the digestion of lipids

Answer 29

• Lipids form large globules when they reach the duodenum, with a small SA
• bile salts emulsify the fats into smaller units with larger SA
• salts then create micelles with the products of lipid breakdown and these micelles transport hydrophobic molecules towards enterocytes
• lipids diffuse into enterocytes while bile salts stay in the gut and are reabsorbed in terminal ileum and returned to liver to be reused

Question 30

What is the role of chylomicrons?

Answer 30

• carry digested fat via lymphatics to blood
• inside enterocytes, lipid molecules are re-estefied and packed with apoproteins and these chylomicrons then leave the basolateral membrane of the enterocyte
• as they are too large to enter capillaries, they enter lymphatic capillaries -> thoracic duct

Question 31

What is steatorrhoea?

Answer 31

Bile acids/lipases not secreted in adequate amounts so undigested fat is excreted in faeces - pale, floating and foul smelling