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PHGY 210 > Gastro VIII > Flashcards

Gastro VIII Flashcards

1
Q

What type of pancreatic secretion requires a cofactor to be effective?

A

Pancreatic lipases.

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2
Q

Describe how the pancreatic lipase cofactor gets produced and the effect it has.

A

Co-colipase -> colipase (by trypsin)
Lipids -> fatty acids, di- and mono-glycerides (by colipase and pancreatic lipase)

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3
Q

What is the main secretion of the liver? Where does it get released?

A

It secretes bile salts from hepatic ducts. It travels in the common bile duct and is released into the SI at the same location as pancreatic juice.

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4
Q

Describe the osmolarity, composition, and pH of liver bile.

A

Isotonic, alkaline, HCO3- dominant

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5
Q

What are the 4 components of the liver bile? Does it contain digestive enzymes?

A
  • Bile salts
  • Bile pigments
  • Cholesterol
  • Phospholipids
    NO digestive enzymes
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6
Q

When is bile secreted by the liver? How much gets released per day?

A

Bile secretion by the liver is continuous. Releases about 0.5-1.0 L/day

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7
Q

How much bile enters the duodenum per day? What is the reason for this?

A

Entrance of bile into the duodenum is intermittent. The volume of bile entering the SI is < 500-700 ml per day because a lot of it is stored in the gallbladder.

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8
Q

What is the function of the gallbladder?

A

It stores and concentrates bile salts. It does NOT synthesize bile salts.

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9
Q

How does the concentration of bile salts change before and after being in the gallbladder?

A

Goes from 3% in the hepatic bile to 10-20% in gallbladder bile. The viscosity increases as well.

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10
Q

How does the pH of bile salts change after being stored in the gallbladder?

A

Goes from 7.8-8.2 in the hepatic bile to 7-7.5 in the gallbladder bile (becomes more acidic, pH reduced)

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11
Q

What is the cause of gallstones?

A

They are caused by not having enough bile salts, which will cause cholesterol to precipitate.

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12
Q

What is the effect of getting a cholecystectomy?

A

This is the removal of the gallbladder. You won’t have concentrated bile salts. This is ok as long as you don’t have very fatty meals. The liver bile will be sufficient for processing the meal.

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13
Q

Bile salt are made of […]

A

cholesterol

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14
Q

What are the 3 functions of bile salts?

A

They facilitate the digestion, traensport, and absorption of FAT (including cholesterol) by forming water-soluble complexes with the fats.

They also facilitate the transport and absorption of fat-soluble vitamins, such as A, D, E, and K.

They also reduce surface tension of lipid contents and stabilize emulsions.

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15
Q

What is the polarity of bile salts?

A

They are amphipathic molecules.

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16
Q

What are micelles and mixed micelles?

A

Micelles are bile salts arranged in a structure with non-polar surfaces facing in and polar surfaces facing out. Mixed micelles are micelles with fats inside.

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17
Q

Explain why the formation of micelles helps with fat breakdown.

A

The micelles keep the fat from precipitating out and allow it to be stored in smaller droplets - stable emulsions. These have a smaller surcace area to volume ratio that makes them easier to break down.

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18
Q

How much bile salt is present in the total pool? How much gets synthesized and released per day? Explain why this is.

A

Bile salt pool: 3.5 g
Daily synthesis: 0.5 g
Daily release into intestine: 15-20 g
The bile salt pool gets recirculated several times a day, and it gets mostly reabsorbed and returned to the liver.

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19
Q

Bile salt gets reabsorbed and transported via the […]. Describe the path it follows.

A

enterohepatic circulation. Bile salts circulate between the liver and the SI and then back to the liver. They get reabsorbed in the SI by the enterohepatic circulation.

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20
Q

What are the 2 intraportal functions of bile salt?

A
  1. Regulate the volume of bile secreted by the liver
  2. Regulate the synthesis of new bile salts
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21
Q

Explain how bile salts regulate hepatic bile flow.

A

The more bile salt returned via portal blood, the larger the volume of bile secretion. This is a positive feedback.

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22
Q

How is bile volume affected if the ileum is removed?

A

If we didn’t have the ileum, bile salt wouldn’t be able to be reabsorbed. This would mean that the volume of bile secreted is going to decrease (regulation of hepatic bile flow)

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23
Q

Explain how bile salts regulate the synthesis of new bile salts.

A

The more bile salt returned in the portal blood, the smaller the amount of NEW bile salt being synthesized. This is a negative feedback.

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24
Q

What happens to the synthesis of bile salts if the ileum is removed?

A

Bile salt synthesis would increase due to the negative feedback in the intraportal regulation of synthesis.

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25
Q

Name an intrahepatic function of bile salts.

A

Keeping cholesterol in solution, increasing its solubility by 2 x 10^6

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26
Q

Name an intraintestinal function of bile salts.

A

Emulsifies and transports fats.

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27
Q

Describe the two ways in which bile salts assist in intestinal transportation and emulsification of fats.

A
  1. Acts as detergents and help form stable emulsions
  2. Assists in the transport of fat and fat-soluble vitamins A, D, E, K from SI lumen into intestinal cell
28
Q

Name an intracolonic function of bile salt.

A

Prevents too much water absorption.

29
Q

Explain how bile salts prevent excess water absorption in the colon.

A

They inhibit Na+ transport and H2O absorption.

30
Q

What happens if bile salts inhibit Na+ and H2O absorption excessively? What about insufficiently?

A

If we keep too much of these bile salts and prevent Na/water absorption too much, we get diarrhea. If we don’t keep enough, we’ll get constipation.

31
Q

What are the two types of cells that secrete from the pancreas?

A

Contains cells that release:
- A large volume of juice rich in HCO3-
- A small volume of juice rich in enzymes

32
Q

What are choleretics?

A

Agents which cause the liver to secrete a larger volume of bile.

33
Q

What are cholagogues?

A

Agents which cause an increase in gallbladder emptying.

34
Q

What is the law of reciprocal activity?

A

If the gallbladder is contracted, the sphincter of Oddi will be relaxed and vice versa.

35
Q

How does the activation of the vagus nerve in the cephalic phase of secretion affect:
a) Liver secretions
b) Gallbladder contraction and sphincter relaxation
c) Pancreas low volume/high enzyme/low pH secretion
d) Pancreas high volume/low enzyme/high pH secretion

A

a) Increases slightly
b) Increases a lot (in anticipation of meal)
c) Increases a lot
d) Does not affect

36
Q

How does gastrin in the gastric phase of secretion affect:
a) Liver secretions
b) Gallbladder contraction and sphincter relaxation
c) Pancreas low volume/high enzyme/low pH secretion
d) Pancreas high volume/low enzyme/high pH secretion

A

All will increase slightly.

37
Q

How does CCK release affect:
a) Liver secretions
b) Gallbladder contraction and sphincter relaxation
c) Pancreas low volume/high enzyme/low pH secretion
d) Pancreas high volume/low enzyme/high pH secretion

A

a) Does not affect
b) Increases a lot (CCK leads to contraction of gallbladder)
c) Increases a lot
d) Does not affect

38
Q

Under what specific circumstances does CCK tend to be released?

A

When we have a protein-rich or fat-rich meal

39
Q

Under what specific conditions does secretin tend to be released?

A

When there are very acidic contents in the SI.

40
Q

How does the release of secretin affect:
a) Liver secretions
b) Gallbladder contraction and sphincter relaxation
c) Pancreas low volume/high enzyme/low pH secretion
d) Pancreas high volume/low enzyme/high pH secretion

A

a) Increases secretion of bicarbonate ions
b) Does not affect
c) Does not affect
d) Increases a lot

41
Q

How does the release of bile salts affect:
a) Liver secretions
b) Gallbladder contraction and sphincter relaxation
c) Pancreas low volume/high enzyme/low pH secretion
d) Pancreas high volume/low enzyme/high pH secretion

A

a) Increases a lot
b) Does not affect
c) Does not affect
d) Does not affect

42
Q

Describe the state of fat, carb, and protein breakdown as a result of salivary, gastric, pancreatic, and hepatic secretions. Include what enzymes are responsible.

A

Polysaccharides -> disaccharides (by salivary and pancreatic amylase)
Proteins -> small peptides (pepsin, trypsin, chymotrypsin)
Fats -> mono, diglycerides, FAs (lipase, co-lipase, bile salts)

43
Q

The final steps in digestion are mediated by […]. Where does this occur?

A

intestinal enzymes. This occurs at the site where absorption takes place.

44
Q

Where are the intestinal enzymes necessary for digestion located? What are they called?

A

They are attached to the microvilli of SI epithelial cells. They are called brush border enzymes.

45
Q

What parts of the GIT have increased surface area?

A

Stomach and small intestine

46
Q

What is the function of the crypt region in the SI?

A

Crypt cells lack digestive enzymes, but secrete a large volume of alkaline fluid known as succus entericus.

47
Q

What is the function of the villus region in the SI?

A

Has cells called enterocytes that complete digestion and absorb the nutrients. They do not secrete fluid.

48
Q

Describe the composition, osmolarity, and pH of succus entericus.

A

Isotonic, HCO3- dominant, alkaline

49
Q

What is the main enzyme secreted by enterocytes? Where does this happen? What is their function?

A

Enterokinase. This is secreted in the small intestine in the brush border. The function of enterokinase is to catalyze trypsinogen to trypsin, which can then catalyze the other digestive enzymes.

50
Q

Explain how cell turnover occurs in the SI.

A

New cells are produced in the crypt region and migrate up to the villus region, maturing along the way. Meanwhile, cells at the tip eventually apoptose and slough into the lumen. This turnover takes around 3-5 days.

51
Q

Describe how fats, carbohydrates, and sugars get absorbed in the villus.

A

Carbohydrates and sugars are absorbed via the capillary and travel through the blood and the hepatic portal vein until they reach the liver and then the heart.

Fats are absorbed at the level of the lacteal, and the nutrients will form complexes called chylomicrons. They will move into the lymphatic system and eventually the large veins of the chest.

52
Q

Where is digestion and absorption of nutrients completed?

A

The small intestine.

53
Q

Does the colon secrete a lot? What is the composition of its secretion?

A

No, it only secretes a small volume. This secretion is alkaline and contains lots of mucin. It has no digestive enzymes and does not contribute to the absorption of nutrients.

54
Q

What part of the GIT has bacterial activity? What process is its regulation associated with?

A

The colon. The MMC is important in keeping bacteria in the colon and not allowing it to migrate into the SI.

55
Q

What are the ways in which intestinal secretions can be regulated?

A
  • Local enteric reflexes
  • Vago-vagal reflexes
  • Hormonal factors
56
Q

Most of the absorption in the GIT is […]

A

reabsorption

57
Q

What is the fate of the enzymes released into the GIT via secretion after they have served their purpose?

A

They get broken down into amino acids and return to the a.a. pool.

58
Q

What is the only GI organ essential to life? Explain why.

A

The small intestine, because nutrient absorption occurs there and it is impossible for another organ (i.e. the colon) to take over.

59
Q

In the small intestine, how fast or slow is the flow of blood and lymph? Why?

A

The blood flows very quickly (1-2 L per minute) to ensure efficient absorption of carbs and proteins. Lymph flow is much slower (1-2 ml per minute) because this is adequate for fats to be absorbed.

60
Q

State the major areas of absorption for the following substances in the SI:
a) Iron and calcium
b) CHO
c) Proteins, lipids, Na+, H2O
d) Vitamin B12
e) Bile acids

A

a) Proximal duodenum
b) Whole SI
c) Whole SI
d) Ileum
d) Whole SI but mostly in ileum

61
Q

Why does most water absorption take place in the SI?

A

Because when nutrients are absorbed, water will follow the osmotic gradient generated by the movement of ions and nutrients.

62
Q

What are the 4 possible limits of absorption?

A
  1. Adequate digestion
  2. Adequate sites for absorption
  3. Adequate transit time for absorption
  4. Adequate co-factors, transporters
63
Q

Describe the breakdown of where water absorption takes place in the GIT.

A

7/9 takes place in the Si and 2/9 takes place in the colon.

64
Q

How does the amount of water absorbed by the GIT compare to the maximum amount that we can absorb?

A

In both the SI and colon, we can absorb double the amount of water maximum than we typically do day-to-day

65
Q

What is the cause of lactose intolerance?

A

The lack of the brush border enzyme lactase.

66
Q

Compare the transit times as you go along the GIT.

A

Pharynx: <1 second
Esophagus: seconds
Stomach: minutes-hours
SI: several hours
Colon: hours-days

PHGY 210 (36 decks)

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