9 Chyme, Pancreas and Liver Secretions

Question 1

Why is it important that water moves into the duodenum?

Answer 1

Chyme entering duodenum is hypertonic- water deals with hypertonicity

Question 2

When the chyme leaves the duodenum is it hypertonic, isotonic or hypotonic?

Answer 2

Isotonic (generally)

Question 3

What are the Brunner’s glands and what do they do?

Answer 3

Question 4

Why is it important that chyme release into the duodenum is controlled?

Answer 4

Stomach impermeable to water

Duodenum is relatively permeable to water

Hypertonic chyme draws water from ECF/circulation into duodenum

Must be controlled so as not to overwhelm duodenum

Question 5

Secretions from the pancreas and liver allow for further digestion of chyme, what are these secretions (in general terms)?

Answer 5

Question 6

What 2 hormones does the duodenum secrete in response to the presence of chyme and what effects do these hormones have?

Answer 6

Question 7

Pancreatic secretions are stimulated by secretin and CCK. What else are they stimulated by?

Answer 7

Autonomics

Sympathetic inhibits

Parasympathetic (vagus) stimulates

Question 8

The following diagram shows an acinus found within the pancreas. Which cells release the enzymatic components and which cells release the aqueous bicarbonate component?

Answer 8

Question 9

Label the parts of the pancreas:

Answer 9

Question 10

CCK and the vagus stimulate acini within the pancreas to produce enzymes. What enzymes and state whether they are active of inactive?

Answer 10

Proteases:

• Trypsin
• Chymotrypsin
• Elastase
• Carboxypeptidase

Question 11

If proteases become activated whilst inside the pancreas, what will they cause?

Answer 11

Pancreatitus

Question 12

How much bile does the liver secrete per day?

Answer 12

250ml-1000mL per day

Question 13

In general terms, what does bile consist of? (3)

Answer 13

1. Bile acids
2. Bile pigments
3. Alkaline solution

Question 14

Through which vein does all of the blood from the gut drain into the liver?

Answer 14

Through portal vein

Question 15

Identify each of the anatomical lobes in the following image and where the falciform ligament is.

Answer 15

Question 16

What are the components of the portal triad?

Answer 16

Question 17

Where do the central veins running through the centre of the liver lobules drain into?

Answer 17

Hepatic veins

Question 18

Outline the flow of blood and the flow of bile within the liver lobules

Answer 18

Question 19

Which zone in the acinus in the following diagram is most vulnerable to:

ischaemic damage?

toxic damage?

Answer 19

Ischaemic: zone 3

Toxic: zone 1

Question 20

In which cells is bile created?

Answer 20

Hepatocytes and duct cells in liver

Question 21

Why does bile need to be stored in the gall bladder?

Answer 21

Bile= continuously produced but only needed intermittently so stored

Question 22

What are the functions of bile?

Answer 22

Emulsify fats- increase SA- aiding digestion

Allows waste products from blood to be excreted

Question 23

Why are bile acids converted to bile salts? How do the bile salts aid lipid digestion?

(Converted by addition of amino acids eg glycine and taurine)

Answer 23

Bile acids- not very soluble in stomach acid

Bile salts have amphipathic structure so act as oil/water interface- create micelles with products of lipid breakdown

Micelles transport digested lipids to luminal membrane of enterocyte- lipids diffuse in, bile salts do not

Question 24

Outline the recycling of bile salts.

Answer 24

Bile salts remain in gut (not taken up by enterocytes)

Reabsorbed in terminal ilium

Return to liver via portal blood

Question 25

What is steatorrhoea and how might it be caused?

Answer 25

• Steatorrhoea: undigested fat appearing in faeces
  
  • Pale, floating, foul smelling
• Causes:
  
  • Lipid not emulsified with bile
    
    • Bile not getting into duodenum
  • Problem with enzymes in pancreas