Physiology of the Pancreas and Liver

Question 0

How are the features of chyme leaving the stomach corrected?

Answer 0

Acidity corrected by HCO3 secreted from the pancreas, liver and duodenal mucosa
Hypertonicity corrected by osmotic movement of wager across the duodenal wall
Digesting competed by enzymes from the pancreas and small intestine mucosa, bile acids from the liver

Question 1

What are the properties of chyme leaving the stomach?

Answer 1

Acidic
Hypertonic
Partially digested

Question 2

How much bile is secreted by the liver a day?

Answer 2

0.25-1.0L/day

Question 3

What does the bile acid dependent component of bile contain?

Answer 3

Bile acids

Pigments

Question 4

Which cells is the bile-acid dependent component secreted by?

Answer 4

Cells lining the canaliculi

Question 5

Give the structure of bile acids/salts and how they travel

Answer 5

Made up of cholic acid and chenodeoxycholic acid
-derivatives of cholesterol

Conjugated to amino acids
Travel as micelles - hydrophilic ends on outside

Also made up of cholesterol and bilirubin

Question 6

What is the bile acid independent component of bile made up of and by which cells is it secreted?

Answer 6

Secreted by duct cells (cells lining intra-hepatic bile ducts)
Alkaline juice - HCO3-

Question 7

What makes up the portal triad?

Answer 7

Arteriole - branch of the hepatic artery
Venule - branch of the hepatic portal vein and drains into the central vein
Duct - branch of the bile duct leaving the liver

Question 8

What are micelles made up of?

Answer 8

Cholesterol at the core

Bile acids and phospholipids

Question 9

What does bile do to fats in the small intestine?

Answer 9

Congregates around the fat (hydrophilic ends sticking out) to form a micelle. Breaks down the fat globule into smaller ones, allowing a a larger surface area for pancreatic enzymes to digest it.

Question 10

What do pancreatic lipases do?

Answer 10

Cleave triacylglycerols into fatty acids and glycerol

Question 11

What happens to the released fatty acids?

Answer 11

They form micelles which are 4-6nm in diameter
With polar groups of bile acids on outside and hydrophobic fatty acids in the middle.
The micelles carry the fatty acids to the unstirred layer where the fatty acids can be absorbed by the cells

Question 12

What happens to the fatty acids once they are inside the epithelial cells?

Answer 12

They are reconstituted as triacylglycerols

Re-expelled as chylomicrons

Question 13

What does the alkaline part of the bile do?

Answer 13

Helps to neutralise the chyme coming in from the stomach

Question 14

What causes the release of bile?

Answer 14

In response to stomach emptying, cholecystokinin is secreted (CCK)
This caused contraction of the gall bladder and ejection of concentrated bile acids together with pancreatic enzymes

Question 15

What is the path that bile acids from the liver travel down?

Answer 15

Hepatocytes - canaliculi - interlobular biliary ducts - collecting bile ducts - right and left hepatic ducts - common hepatic duct - common bile duct - ampulla of Vater - duodenum - terminal ileum

Question 16

How are bile acids recycled?

Answer 16

Venous return from the gut enters the hepatic portal vein where hepatocytes actively take up bile acids.
Can then re-secrete them into the canaliculi.

Question 17

Where are bile acids stored?

Answer 17

Gall bladder

Question 18

How is the volume of bile acids needed to be stored reduced?

Answer 18

Bile acids are concentrated

Salt and water are transported across the gall bladder epithelium

Question 19

What does concentration of bile acids increase the risk of?

Answer 19

Precipitation leading to gall stones

Question 20

What increases the risk of gall stones?

Answer 20

Age
Pregnancy
Obesity
More common in women

Question 21

What are the symptoms of gall stones if they are in the gallbladder, neck or biliary tree?

Answer 21

Gall bladder - usually asymptomatic

Neck and biliary tree - biliary colic and obstruction, inflammation (cholecystitis) and infection of the gall bladder

Question 22

What are used to treat gall stones?

Answer 22

Cholecystectomy - removal of gall stones
Pain killers
Antibiotics

Question 23

With gallstones, when is the pain often worse and why?

Answer 23

After eating

CKK is released causing contraction of the gall bladder

Question 24

What does the exocrine pancreas secrete?

Answer 24

Proteases including trypsinogen, chymotrypsin, elastase, carboxypeptidase
Amylases
Lipases
Alkaline juice

Question 25

How are enzymes secreted from the acini of the pancreas?

Answer 25

Synthesised as inactive precursors
Packaged into condensing vacuoles by Golgi to form zymogen granules which are secreted by exocytosis
Then activated in the small intestine by enzymatic cleavage

Question 26

What is released into the blood in pancreatitis?

Answer 26

Amylase

Question 27

What is acinar secretion of the pancreas stimulated by and where is this released from?

Answer 27

CCK which released from duodenal APUD cells stimulated by hypertonicity and fats
Vagus nerve by Ach in response to cephalic phase - food being put in mouth

Question 28

Where is HCO3 secreted from in the pancreas?

Answer 28

Duct cells

Question 29

Mechanism of secretion of HCO3- from the pancreas?

Answer 29

Na-ATPase sets the gradient
H+ exported into ECF from cell using Na gradient via Na-H exchange
In ECF - H+ + HCO3- -> H2O + CO2 
Products taken up into cell
H2O + CO2 -> H+ + HCO3- inside cell
HCO3 exporter into duct lumen
H+ recycled

Question 30

What stimulates secretion of HCO3 from duct cells of pancreas?

Answer 30

Secretin released from jejunal cells
Released in response to low pH
CKK also aids secretin secretion

Question 31

How does steatorrhoea form?

Answer 31

If bile salts/pancreatic enzymes are not secreted in adequate amounts, fat appears in faeces

Question 32

Features of steatorrhoea?

Answer 32

Pale
Floating
Smelly