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Flashcards in Week 6 - Pancreas and Liver Deck (54):
1

How is the chyme made isotonic?

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

2

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

-Bicarb
-Enzymes

3

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

-Bile
-Bicarb

4

Why is chyme hypertonic as it leaves the stomach?

-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

5

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

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

6

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

-Acini -> secrete enzymes
-Ducts -> modify aqueous secretions

7

Describe the effects of the symp and parasymp on pancreas?

-Symp inhibits
-Parasymp stimulates

8

What proportion of the pancreas is exocrine?

-90%

9

What specifically stimulates pancreatic acinar?

-Vagus nerve
-Cholecystikinin

10

What causes the release of CCK?

-Detection of hypertonic chyme and fats in duodenum

11

What are the main enzymes are produced by acinar cells?

-Amylases/Lipases
-Proteases -> trypsin, chymotrypsin, elastase, carboxypeptidase

12

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

-Proteases

13

Briefly describe the synthesis of pancreatic enzymes

-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

14

Why are proteases secreted in an inactive form?

-To prevent pancreatic digestion

15

What does amylase in the blood signify?

-Pancreatic damage

16

Describe the solution produced by pancreatic ductal cells

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

17

What stimulates ductal cells to secrete HCO3?

-Secretin

18

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

-Increased HCO3 secretion

19

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

-Neutralise acidic chyme

20

What are the three major functions of the liver?

-Energy metabolism
-Detoxification
-Plasma protein production

21

What is the functional cell of the liver?

-Hepatocyte

22

How are hepatocytes specialised for their function?

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

23

What is a structural unit of the liver?

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

24

Describe a liver lobule

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

25

What makes up a portal triad?

-Hepatic artery
-Portal vein
-Bile duct

26

What is the functional unit of the liver? Describe this

-Acinus
-Diamond shape formed between two central veins of adjacent lobules
-Separated into 3 zones from outside to in

27

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

-Zone 1 (closest to hepatic artery)

28

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

-Zone 3

29

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

-Zone 1

30

What are bile canaliculi?

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

31

What is the fate of central veins of liver lobules?

-Unite and form 3 hepatic veins which drain into IVC

32

What is the portal vein?

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

33

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

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

34

What are the two components of bile?

-Bile acid dependant
-Bile acid independent

35

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

-Contains bile acid and pigments
-Secreted by hepatocytes into canaliculi

36

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

-Aqueous alkaline secretion
-Secreted by ductal cells

37

What stimulates bile duct cells to secrete its aqueous solution?

-Secretin

38

What are the two primary bile acids?

-Cholic acid
-Chenodeoxycholic acid

39

What is a bile salt?

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

40

Why does conjugation of bile acids need to occur?

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

41

What makes bile salts soluble at duodenal pH?

-Amphipathic structure

42

What is the function of bile?

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

43

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

-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

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

-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

What happens to the bile salts in the intestinal lumen?

-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

What is the function of the gall bladder?

-Stores and concentrated bile by removing water and ions

47

What stimulates gall bladder contraction?

-CCK released from duodenum

48

What effect does CCK have on sphincter of oddi?

-Relaxes it

49

What is steatorrhoea?

-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

What is bilirubin?

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

51

What happens to bilirubin once it is formed?

-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

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

-Gall stones

53

What is different about the jejunum and ileum?

-Jejunum is thick walled ileum is thin

54

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

-Hypertonic