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GI > Week 6 - Pancreas and Liver > Flashcards

Week 6 - Pancreas and Liver Flashcards

1
Q

How is the chyme made isotonic?

A

-Water from ECF is drawn in and chyme is isotonic by the time it passes the pancreas

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2
Q

What two secretions are produced by the pancreas which alter chyme?

A
  • Bicarb

- Enzymes

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3
Q

What two secretions are produced by the liver which alter chyme?

A
  • Bile

- Bicarb

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4
Q

Why is chyme hypertonic as it leaves the stomach?

A
  • Food produces lots of solutes which are dissolved in gastric juice
  • Water cannot be added to dilute solute in chyme as the stomach is impermeable to water
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5
Q

Why does hypertonicity of chyme begin to change as soon as it enters the duodenum?

A

-Duodenum is permeable to water so water is drawn into the lumen

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6
Q

What are the basic structures of the exocrine pancreas and there respective functions?

A
  • Acini -> secrete enzymes

- Ducts -> modify aqueous secretions

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7
Q

Describe the effects of the symp and parasymp on pancreas?

A
  • Symp inhibits

- Parasymp stimulates

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8
Q

What proportion of the pancreas is exocrine?

A

-90%

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9
Q

What specifically stimulates pancreatic acinar?

A
  • Vagus nerve

- Cholecystikinin

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10
Q

What causes the release of CCK?

A

-Detection of hypertonic chyme and fats in duodenum

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11
Q

What are the main enzymes are produced by acinar cells?

A
  • Amylases/Lipases

- Proteases -> trypsin, chymotrypsin, elastase, carboxypeptidase

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12
Q

Which enzymes are secreted in an inactive form from the pancreas?

A

-Proteases

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13
Q

Briefly describe the synthesis of pancreatic enzymes

A
  • Formed on rough ER and moved to golgi complex for modification, processing and packaging
  • Condensed into vacuoles
  • Concentrated in zymogen granules
  • Released in response to stimulus
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14
Q

Why are proteases secreted in an inactive form?

A

-To prevent pancreatic digestion

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15
Q

What does amylase in the blood signify?

A

-Pancreatic damage

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16
Q

Describe the solution produced by pancreatic ductal cells

A

-Aqueous solution which is isotonic and contains Na, K, Cl and HCO3

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17
Q

What stimulates ductal cells to secrete HCO3?

A

-Secretin

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18
Q

What is the effect on HCO3 production of increased flow rate of pancreatic juice?

A

-Increased HCO3 secretion

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19
Q

What is the purpose of the aqueous solution produced by pancreatic ductal cells?

A

-Neutralise acidic chyme

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20
Q

What are the three major functions of the liver?

A
  • Energy metabolism
  • Detoxification
  • Plasma protein production
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21
Q

What is the functional cell of the liver?

A

-Hepatocyte

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22
Q

How are hepatocytes specialised for their function?

A

-Contain high amounts of rER and sER, golgi stacks and glycogen

23
Q

What is a structural unit of the liver?

A

-Lobule of hepatocytes surrounded by connective tissue which has invaginated from the capsule

24
Q

Describe a liver lobule

A

-Usually hexagonal collection of hepatocytes with a central vein and many portal triads at the corners

25
Q

What makes up a portal triad?

A
  • Hepatic artery
  • Portal vein
  • Bile duct
26
Q

What is the functional unit of the liver? Describe this

A
  • Acinus
  • Diamond shape formed between two central veins of adjacent lobules
  • Separated into 3 zones from outside to in
27
Q

Which zone of a functional unit of the liver is most oxygenated?

A

-Zone 1 (closest to hepatic artery)

28
Q

Which zone of the functional acinus of liver is most susceptible to hypoxia?

A

-Zone 3

29
Q

Which zone of the functional acinus of liver is most susceptible to toxins?

A

-Zone 1

30
Q

What are bile canaliculi?

A

-Bile canals which flow out towards the bile ducts in the portal triad

31
Q

What is the fate of central veins of liver lobules?

A

-Unite and form 3 hepatic veins which drain into IVC

32
Q

What is the portal vein?

A

-The vein which drains all the blood from the gut and takes it to the liver for detoxification

33
Q

What is the relationship between blood and bile in the liver?

A
  • Blood from portal vein and hepatic arteries flows in towards the central vein
  • Bile flows out along canaliculi to bile duct
  • > opposite direction
34
Q

What are the two components of bile?

A
  • Bile acid dependant

- Bile acid independent

35
Q

What is the bile acid dependant component of bile and from where is it secreted?

A
  • Contains bile acid and pigments

- Secreted by hepatocytes into canaliculi

36
Q

What is the bile acid independent component of bile and from where is it secreted?

A
  • Aqueous alkaline secretion

- Secreted by ductal cells

37
Q

What stimulates bile duct cells to secrete its aqueous solution?

A

-Secretin

38
Q

What are the two primary bile acids?

A
  • Cholic acid

- Chenodeoxycholic acid

39
Q

What is a bile salt?

A

-Bile acids which are conjugated with the amino acids glycine or taurine

40
Q

Why does conjugation of bile acids need to occur?

A

-At duodenal pH bile acids are not soluble but bile salts are

41
Q

What makes bile salts soluble at duodenal pH?

A

-Amphipathic structure

42
Q

What is the function of bile?

A

-Lipids form large globules by the time they enter duodenum -> bile emulsifies dietary lipids in order to increase SA for lipase

43
Q

How are fats absorbed?What happens once they are absorbed?

A
  • Products of lipid breakdown eg cholesterol, FAs form micelles with bile acids which then diffuse through aqueous solution to microvilli brush border and the products then diffuse into enterocytes
  • Inside the cell the lipid products are re-esterified and packaged with apoproteins to form chylomicrons
44
Q

What happens to the chylomicrons which are formed in the enterocytes?

A

-Exocytosed from basolateral membrane but are too large to enter capillaries so enter lacteals and travel through lymphatic system to re-enter vascular circulation through the thoracic duct into left subclavian vein

45
Q

What happens to the bile salts in the intestinal lumen?

A
  • Dont enter enterocytes instead remain in gut lumen and travel to terminal ileum
  • Reabsorbed in terminal ileum and returned to the liver in portal blood
46
Q

What is the function of the gall bladder?

A

-Stores and concentrated bile by removing water and ions

47
Q

What stimulates gall bladder contraction?

A

-CCK released from duodenum

48
Q

What effect does CCK have on sphincter of oddi?

A

-Relaxes it

49
Q

What is steatorrhoea?

A

-Pale, floating and foul smelling stool due to fat in the faeces caused by bile acids or pancreatic lipase being secreted in inadequate amounts

50
Q

What is bilirubin?

A

-An excretory bile pigment produced as a breakdown products of Hb

51
Q

What happens to bilirubin once it is formed?

A
  • Conjugated in the liver to make it soluble and then secreted into bile
  • It is excreted in the faeces as stercobilin or in the urine as urobilinogen
52
Q

What can result from concentration of bile in the gall bladder?

A

-Gall stones

53
Q

What is different about the jejunum and ileum?

A

-Jejunum is thick walled ileum is thin

54
Q

What is the osmolarity status of the chyme when it leaves the stomach?

A

-Hypertonic

GI (16 decks)

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