Pancreas and Liver Flashcards
Which glands of the duodenum secrete alkaline fluid to neutralise acidic chyme?
Brunner’s Glands
Explain why chyme is hypertonic
The stomach is largely impermeable to water so chyme cannot be diluted
How does water move when chyme enters the duodenum? Explain why
Water from ECF/ circulation moves into the duodenum to make the hypertonic chyme more isotonic
Why must chyme release into the dudenum be controlled?
So as not to overwhelm the duodenum
Which hormones act on the pancreas to cause it to release its secretions?
- CCK acts of pancreas → stimulates enzymatic componenet of secretion
- Secretin acts on pancreas → stimulates HCO3- (aq) to neutralise acidic chyme
What stimulates the release of secretin from the duodenum?
The presence of acidic chyme entering from the stomach
How are pancreastic secretions controlled by autonomics?
- Sympathetics inhibit
- Parasympathetic stimulates (via vagus nerve)
Where in the pancreas are enzymes produced?
Produced in acini
How are proteases stored in the pancreas? What would be the consequence of they were not stored in this way?
Proteases are stored in their inactive form in zymogen granules
If they weren’t inactive they would start to digest the pancreas → pancreatitis
Which cells of the pancreas secrete the aqueous component and bicarbonate?
Duct Cells
How do pancreatic secretions reach the duodenum?
Via the pancreatic duct and the ampulla of Vater
What does the liver secrete in response to chyme?
Bile
What components make up bile?
- Bile acids
- Bile pigments
- Alkaline solution
What is the main functional unit of the liver?
Hepatocyte
What is the role of bile?
Emulsifies fat so they can be readily digested by lipases secreted by the pancreas
How many lobes is the liver split into and what separates them?
2 lobes separated by the falciform ligament
How is the liver arranged microscopically?
Hexagonal arrangements of hepatatic triads towards a central hepatic venule
Each triad consists of:
- Bile Duct
- Branch of portal vein
- Branch of Hepatic artery
In which directions do blood and bile flow in the haptic triad?
- Blood - towards central vein via sinusoids
- Bile- opposite direction along canaliculi into the duodenum
Which zones of the liver will be damaged in
a) Ischemia
b) Toxicity
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
How does the compostion of bile change as it is stored in the gallbladder?
How can this lead to certain pathologies?
Bile becomes more concentrated as water/ ions are removed
This can lead to gallstones
What are bile salts? How do they differ from bile acids?
Conjugated Bile Acids
They are amphipathic and more soluble at duodenal pH than bile acids
Explain how bile salts emulsify fats
- Bile salts emulsify large drops of fat into smaller units to increase surface area fro lipases to act on
- Bile salts create micelles with the products of lipid breakdown
- Micelles transport the hydrophobic molecules of digestion towards the enterocyte
Are bile salts are not absorbed into the enterocyte, explain what happens to them after they have delivered micelles to the intestinal cell
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
What happens to lipids once they enter the enterocyte?
- 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
What is steatorrhoea, how is it caused?
Steatorrhoea = fatty poo
Certain pathologies cause bile acids/salts or pancreatic lipases to be produced in insufficient amounts
Undigested fat appears in faeces
