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GI system > Liver and pancreas > Flashcards

Liver and pancreas Flashcards

1
Q

What does the stomach release into the duodenum?

A

Chyme

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2
Q

What are the properties of chyme?

A

Low pH, acidic

Hypertonic

Partially digested

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3
Q

Why is chyme acidic?

A

Mixed with gastric acid in the stomach

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4
Q

Why is chyme hypertonic?

A

Digestion produces small molecules that are osmotically active
increased number of osmoles

Stomach wall is impermeable to water
so water cannot enter lumen of stomach to dilute the chyme

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5
Q

What protects the epithelial cells of the duodenum from the acidity of the chyme released into it?

A

Mucus containing bicarbonate ions
secreted by goblet cells in crypts
and brunner’s glands

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6
Q

What happens to the tonicity of the chyme in the duodenum?

A

Becomes isotonic

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7
Q

How does the chyme become isotonic in the duodenum?

A

The duodenum wall is permeable to water
water moves from extracellular fluid of duodenum into its lumen
dilutes the chyme

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8
Q

What happens to the pH of the chyme in the duodenum?

A

Increases to neutral pH

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9
Q

How is the chyme neutralised in the duodenum?

A

Pancreatic ductal cells secrete solution containing bicarbonate into duodenum

Bile ductal cells secrete alkaline solution in bile into gall bladder and then duodenum

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10
Q

What happens to partially digested molecules in the small intestines?

A

They are fully digested in the small intestines

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11
Q

How are partially digested molecules fully digested in the small intestines?

A

Pancreatic acinar cells secrete enzymes into duodenum

these contribute to completing digestion

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12
Q

When are pancreatic and liver secretions released into the duodenum?

A

When chyme is in the duodenum

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13
Q

What causes the pancreas and liver to release their secretions into the duodenum when chyme is in the duodenum?

A

When chyme is in the duodenum

the duodenum secretes secretin and cholecystokinin (CCK)

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14
Q

What are the functions of secretin?

A

Acts on the pancreatic ductal cells
to stimulate them to secrete bicarbonate solution into the duodenum

Acts on bile ductal cells
stimulates them to secrete alkaline solution in bile

Acts on parietal cells in the stomach
inhibits their secretion of hydrocloric acid

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15
Q

What are the functions of CCK?

A

Acts on the pancreatic acinar cells
to stimulate them to secrete enzymes into the duodenum

Acts on the gall bladder
stimulates the gall bladder to contract to release bile into the duodenum

Acts on the sphincter of Oddi
causes it to relax to allow passage of liver and pancreatic secretions into major duodenal papilla

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16
Q

What enzymes do acinar cells of the pancreas produce?

A

Amylases

Lipases

Proteases

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17
Q

How active are the amylases, lipases and proteases produced by acinar cells of the pancreas?

A

Amylases and lipases are active

Proteases are inactive

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18
Q

How are the proteases produced by the pancreatic acinar cells inactive?

A

They are produces as zymogens

and are contained in zymogen granules in the acinar cells, pancreatic duct

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19
Q

Why are protease enzymes produced by pancreatic acinar cells produced as zymogens?

A

To prevent them from being active in the pancreas

and from digesting the pancreas itself

20
Q

What happens when protease enzymes produced by pancreatic acinar cells become active in the pancreas?

A

Digest the pancreas itself

causing it to become inflamed, pancreatitis

21
Q

What is a common cause of pancreatitis?

A

Gall stones blocking the ampulla of vater
which the pancreatic duct feeds into
build up of pancreatic secretions in pancreas
zymogen proteases become active while still in the pancreas

22
Q

When are the zymogen protease enzymes produced by pancreatic acinar cells activated?

A

When they are released into the intestinal lumen

23
Q

What are the different types of protease enzymes produced by the pancreas (when they are active)?

A

Trypsin

Chymotripsin

Elastase

Carboxypeptidase

24
Q

What else stimulates the pancreas to secrete solution containing bicarbonate and enzymes, apart from secretin and CCK?

A

Vagus nerve efferents

25
Q

What inhibits the pancreas from secreting solution containing bicarbonate and enzymes?

A

Sympathetic post-ganglionic nerve fibres

26
Q

What secretes bile?

A

Liver hepatocytes

Bile ductal cells

27
Q

How often to liver hepatocytes and bile ductal cells produce bile?

A

Continuously

28
Q

What happens to new bile produced when it is not being secreted into the duodenum?

A

Stored in the gall bladder

29
Q

What happens to bile in the gall bladder?

A

It becomes concentrated

by water and ions being removed

30
Q

What can over-concentration of bile in the gall bladder lead to?

A

Gall stones

31
Q

What is bile made up of?

A

Bile acids

Bile pigments

Alkaline solution

32
Q

What part of bile do liver hepatocytes secrete?

A

Bile acids

Bile pigments

33
Q

What part of bile do bile ductal cells secrete?

A

Alkaline solution

34
Q

What happens to bile acids?

A

They are conjugated with amino acids

to form bile salts

35
Q

What are the two main bile acids?

A

Cholic acid

Chenodeoxycolic acid

36
Q

What is the purpose of conjugating bile acids with amino acids to form bile salts?

A

Bile salts are more soluble at duodenal pH
compared to bile acids
hence they are more functional

37
Q

What is the function of bile salts in the duodenum?

A

Emulsify lipids

Form micelles with digested lipids

38
Q

What is meant by emulsifying lipids?

A

Disperse large lipid globules into smaller lipid droplets

39
Q

What is the purpose of emulsifying fats?

A

Increase surface area of lipid

more surface area for lipases to act over

40
Q

How do bile salts react to water?

A

They are amphipathic
have hydrophilic part, water-soluble
and hydrophobic part, insoluble in water, lipid-soluble

41
Q

How are bile salts adapted to emulsifying fats?

A

Have both water-soluble and lipid-soluble parts

can act at interface between the two

42
Q

What is the function of micelles produced from bile salts?

A

Transport digested lipids to the apical domain of enterocytes

43
Q

What happens to micelles produced from bile salts at the apical domain of the enterocyte?

A

Digested lipids diffuse from micelle into cytosol of enterocyte

Bile salts remain in the lumen

44
Q

What happens to bile salts remaining in the lumen of the small intestine from micelles?

A

Reabsorbed in the terminal ileum
travel through hepatic portal circulation
back to the liver

45
Q

What is the advantage of bile salts being transported back to the liver?

A

Liver can re-use those bile salts

doesn’t have to produce more

GI system (21 decks)

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