Pancreas and Liver

Question 1

Which glands of the duodenum secrete alkaline fluid to neutralise acidic chyme?

Answer 1

Brunner’s Glands

Question 2

Explain why chyme is hypertonic

Answer 2

The stomach is largely impermeable to water so chyme cannot be diluted

Question 3

How does water move when chyme enters the duodenum? Explain why

Answer 3

Water from ECF/ circulation moves into the duodenum to make the hypertonic chyme more isotonic

Question 4

Why must chyme release into the dudenum be controlled?

Answer 4

So as not to overwhelm the duodenum

Question 5

Which hormones act on the pancreas to cause it to release its secretions?

Answer 5

• CCK acts of pancreas → stimulates enzymatic componenet of secretion
• Secretin acts on pancreas → stimulates HCO₃^- (aq) to neutralise acidic chyme

Question 6

What stimulates the release of secretin from the duodenum?

Answer 6

The presence of acidic chyme entering from the stomach

Question 7

How are pancreastic secretions controlled by autonomics?

Answer 7

• Sympathetics inhibit
• Parasympathetic stimulates (via vagus nerve)

Question 8

Where in the pancreas are enzymes produced?

Answer 8

Produced in acini

Question 9

How are proteases stored in the pancreas? What would be the consequence of they were not stored in this way?

Answer 9

Proteases are stored in their inactive form in zymogen granules

If they weren’t inactive they would start to digest the pancreas → pancreatitis

Question 10

Which cells of the pancreas secrete the aqueous component and bicarbonate?

Answer 10

Duct Cells

Question 11

How do pancreatic secretions reach the duodenum?

Answer 11

Via the pancreatic duct and the ampulla of Vater

Question 12

What does the liver secrete in response to chyme?

Answer 12

Bile

Question 13

What components make up bile?

Answer 13

• Bile acids
• Bile pigments
• Alkaline solution

Question 14

What is the main functional unit of the liver?

Answer 14

Hepatocyte

Question 15

What is the role of bile?

Answer 15

Emulsifies fat so they can be readily digested by lipases secreted by the pancreas

Question 16

How many lobes is the liver split into and what separates them?

Answer 16

2 lobes separated by the falciform ligament

Question 17

How is the liver arranged microscopically?

Answer 17

Hexagonal arrangements of hepatatic triads towards a central hepatic venule

Each triad consists of:

• Bile Duct
• Branch of portal vein
• Branch of Hepatic artery

Question 18

In which directions do blood and bile flow in the haptic triad?

Answer 18

• Blood - towards central vein via sinusoids
• Bile- opposite direction along canaliculi into the duodenum

Question 19

Which zones of the liver will be damaged in

a) Ischemia
b) Toxicity

Answer 19

a) Ischemia = Zone 3

As it’s the furthest away O₂ in arteries

b) Toxicity = Zone 1

As it’s closest to the source of damage

Question 20

How does the compostion of bile change as it is stored in the gallbladder?

How can this lead to certain pathologies?

Answer 20

Bile becomes more concentrated as water/ ions are removed

This can lead to gallstones

Question 21

What are bile salts? How do they differ from bile acids?

Answer 21

Conjugated Bile Acids

They are amphipathic and more soluble at duodenal pH than bile acids

Question 22

Explain how bile salts emulsify fats

Answer 22

1. Bile salts emulsify large drops of fat into smaller units to increase surface area fro lipases to act on
2. Bile salts create micelles with the products of lipid breakdown
3. Micelles transport the hydrophobic molecules of digestion towards the enterocyte

Question 23

Are bile salts are not absorbed into the enterocyte, explain what happens to them after they have delivered micelles to the intestinal cell

Answer 23

Bile salts enter enterohepatic circulation

• they remain in the gut
• and are reabsorbed at the terminal ileum
• they are returned to the liver in portal blood
• The Liver recycles bile salts so it doesn’t have to keep producing them

Question 24

What happens to lipids once they enter the enterocyte?

Answer 24

• lipid molecules built back up (re-esterified) into triglycerides, phospholipids and cholesterol
• Packed into chylomicrons
• Chylomicrons exocytosed as the basolateral membrane
• Too large to enter capillaries so enter lymphatic capillaries by the thoracic duct

Question 25

What is steatorrhoea, how is it caused?

Answer 25

Steatorrhoea = fatty poo

Certain pathologies cause bile acids/salts or pancreatic lipases to be produced in insufficient amounts

Undigested fat appears in faeces