Pancreas And Liver

Question 1

How does the chyme become isotonic?

Answer 1

Hypotonic as enters duodenum as stomach is impermeable to water.

But, duodenum is permeable to water so it draws water in so is isotonic as leaves duodenum.

Question 2

What does secretin do?

Answer 2

Acts on pancreas to stimulate an aqueous bicarbonate (HCO3-) component of the pancreatic secretion

Question 3

What does CCK do?

Answer 3

Acts on pancreas to stimulate release of enzymatic component of pancreatic secretions to help digest proteins and fats.

CCK also acts on gallbladder (contracts) and relaxes sphincter of oddi.

Question 4

What stimulates the release of CCK and secretin?

Answer 4

Chyme

Question 5

What does CCK stimulate the release of?

Answer 5

CCK and vagus stimulate acini to produce enzymes.

-Amylases and lipases (active)

-Proteases (inactive) - so not digest pancreas
 —Trypsin
 —Chymotrypsin
 —Elastase
 —Carboxypeptidase

Question 6

What are zymogen granules?

Answer 6

Granules that store the concentrated protease enzymes (inactive) that are produced within acinar cells.

The zymogen granules contain zymogen (inactive proteases) which is converted to active proteases in intestinal lumen.

Question 7

What do duct cells of the pancreas release?

Answer 7

Aqueous component (isotonic)
Bicarbonate 

They act to neutralise the acidic chyme

Question 8

What does the liver secrete in response to chyme?

Answer 8

Bile (stored in gall bladder) into duodenum.

Question 9

What does bile consist of?

Answer 9

Bile acids and bile pigments

Alkaline solutions

Question 10

What does bile do?

Answer 10

Emulsifying fats (lipids) in duodenum so they can be readily digested by lipases secreted by pancreas

Question 11

Where does all blood from the gut go?

Answer 11

Into the liver via the portal vein

Question 12

What are the lobes of the liver?

Answer 12

Left
Right (bigger)
Caudate
Quadrate

Question 13

What is the micronatomy of the liver?

Answer 13

Lobules - Hexagonal arrangement of hepatocytes, bile ducts and blood vessels.

Sheets of hepatocytes arranged towards a central hepatic venule.

Question 14

Describe the structure of a liver lobule

Answer 14

Hexagonal arrangement

Triad of structures at each corner

• Portal vein
• Hepatic artery
• Bile duct

Central vein in the middle.

Blood enters a lobule via hepatic artery and portal vein.

Question 15

What flows in apposing directions of the liver lobule?

Answer 15

Blood flows in towards the central vein via sinusoids -(Portal vein and hepatic artery)

Bile flows out -along canaliculi, then into the bile duct and into the duodenum.

Question 16

What is the functional area of a lobule called?

Answer 16

Acinus

Question 17

Describe anatomy of acinus

Answer 17

Can be divided into three zones.

1 is closer to middle (to the arterial supply) and 3 on outside.

So, if problem with oxygenation, zone 3 more likely to get ischaemic first whereas if something toxic, zone 1 will be affected first.

Question 18

What stimulates contraction of gallbladder?

Answer 18

CCK

Question 19

What is bile mostly made from?

Answer 19

Bile salts

Bile is created by hepatocytes duct cells in the liver.

Question 20

What are bile salts?

Answer 20

Bile salts are conjugated bile acids. (Conjugated to amino acids)

This is good as bile salts are more soluble at duodenal pH than bile acids.

Bile salts = amphipathic

Question 21

What do bile salts do?

Answer 21

Lipids form large globules by the time they have reached the duodenum.

Bile salts then emulsify fat into smaller units. -Disperse droplets increasing surface area, allowing for lipases to act.

Bile salts then create micelles with products of lipid breakdown

Micelles act as a ‘vehicle’ for transporting hydrophobic molecule (products of lipid digestion) towards enterocytes.

Question 22

Where and how do lipids move?

Answer 22

Micelle transports digested lipids to luminal membrane of enterocytes.

Lipids diffuse into intestinal epithelial cell (cytosol of enterocyte) but bile salts do not.

Question 23

How do bile slats get recycled?

Answer 23

Bile salts remain in the gut (do not enter enterocyte)

But, are reabsorbed in the terminal ileum.

They are then returned to the liver in port blood.

The liver recycles the bile salts they do not have to re-synthesise large volumes.

Question 24

What are chylomicrons and what do they do?

Answer 24

Chylomicrons are formed in enterocytes to carry digested fats into lymphatic system to then reach blood circulation.

Inside enterocyte, lipid molecules are built back up again to triglycerides, phospholipids and cholesterol.

Packed with apoproteins within enterocytes (chylomicrons)

Chylomicrons are then exocytosed from the basolateral membrane of the enterocyte as they are too large to enter capillaries. This means then enter the lymphatic capillaries into the thoracic duct.

Question 25

What is steatorrhoea?

Answer 25

This is when undigested fat appears in faeces. It occurs because certain pathologies cause bile acids / salts or pancreatic lipase to not be secreted in adequate amounts.

• Pale
• Floating
• Foul smelling

Question 26

Where is bile secreted into?

Answer 26

Bile secreted via Common Bile Duct then Ampulla of Vater into Duodenum.