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Physiology. Gastrointestinal Physiology. > The Intestinal Phase of Digestion. > Flashcards

The Intestinal Phase of Digestion. Flashcards

1
Q

When does the intestinal phase of digestion begin?

A

When acidic chyme arrives in the small intestine.

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2
Q

Why are gastric functions inhibited as soon as chyme arrives in the duodenum?

A

So that the duodenum is not overloaded.

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3
Q

What stimulates the inhibition of the gastric functions after food arrives in the small intestine?

A

Distension of small intestine.

High acidity.

High nutrient concentration.

Irritation of intestinal mucosa.

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4
Q

What name is given to the process by which gastric functions are inhibited following the arrival of food into the duodenum?

A

The enterogastric reflux.

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5
Q

What hormones are secreted once cyme arrives in the duodenum?

A

Cholecystokinin.

Secretin.

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6
Q

What is the function of secretin?

A

It reduces gastric secretions.

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7
Q

What is the function of choleocystokinin?

A

It reduces gastric motility.

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8
Q

What stimulates the release of secretin?

A

Low pH in the duodenum.

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9
Q

What stimulates the release of choleocystokinin?

A

Fats and proteins in the duodenum.

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10
Q

What is vomiting?

A

The forceful expulsion of stomach and intestinal contents through the mouth.

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11
Q

What processes will initiate vomiting?

A

Antiperistalsis in the small intestine.

Contraction of the duodenum.

Gastric wall and cardia relax.

Contraction of the abdominal muscles.

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12
Q

Vomiting is a reverse of what process?

A

Swallowing.

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13
Q

What centre of the brain controls vomiting?

A

The vomiting centre.

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14
Q

The vomiting centre receives afferent signals from what 4 areas?

A

Mechano and chemoreceptors in the GI tract.

Viscera that are not in the GI tract.

Extramedullary centres in the brain.

Chemoreceptor trigger zone.

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15
Q

What will stimulate the extrmedullary centre of the brain to induce vomiting?

A

It is psychogenic so it caused by things like motion.

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16
Q

What will stimulate the chemoreceptor trigger zone to induce vomiting?

A

Drugs and toxins etc.

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17
Q

What are 3 major consequences of severe vomiting?

A

Loss of fluid.

Loss of potassium ions.

Loss of hydrogen ions.

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18
Q

How will loss of fluid caused by vomiting affect the body?

A

You get hyovolemia of the blood.

This lowers blood pressure.

This leads to circulatory shock.

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19
Q

How will loss of potassium ions caused by vomiting affect the body?

A

It leads to hypokalemia.

This leads to hyperpolarisation of cell membranes.

This leads to reduced excitability of nerves/muscles.

This causes weakness and hyporeflexia.

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20
Q

How will loss of hydrogen ions caused by vomiting affect the body?

A

It causes metabolic alkalosis.

This leads to hypoventilation.

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21
Q

What animals will not be able to vomit?

A

Rodents and horses.

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22
Q

What are 4 factors that can lead to gastric ulcers?

A

NSAID treatment.

Stress.

Increased histamine secretion.

Helicobacter pylori.

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23
Q

What animals are gastric ulcers common in?

A

Horses (particularly young horses).

Dogs.

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24
Q

What typically causes stomach ulcers?

A

A defect in the gastric mucosal barrier.

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25
Q

What typically causes duodenal ulcers?

A

An overproduction of stomach acid.

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26
Q

What causes non-glandular ulcers in horses?

A

A defect in the gastric mucosal barrier.

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27
Q

What causes glandular ulcers in horses?

A

An overproduction of stomach acid.

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28
Q

Chyme is a mixture of what 3 substances?

A

Polypeptides/oligopeptides.

Large emulsified fat globules.

Dietary carbohydrates.

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29
Q

Can anything in chyme be absorbed?

A

No, the contents of chyme must be broken down further.

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30
Q

What 2 events must occur as soon as chyme enters the duodenum?

A

Neutralisation of acid.

Breakdown of macromolecules into micromolecules.

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31
Q

What organs help with the digestion of chyme?

A

The pancreas.

The liver/gall bladder.

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32
Q

How does the pancreas help digest chyme?

A

It provides buffers and digestive enzymes.

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33
Q

How does the liver/gall bladder help digest chyme?

A

It provides buffers and a fat emulsifier.

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34
Q

How does the mucosa of the small intestine help digest chyme?

A

It provides buffers, digestive enzymes and absorption mechanisms.

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35
Q

What animals do not have a gall bladder?

A

Horses.

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36
Q

What is secreted by the pancreas into the duodenum?

A

Bicarbonate and digestive enzymes.

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37
Q

Why is bicarbonate secreted into the duodenum?

A

To increase pH.

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38
Q

How much bicarbonate is secreted by the pancreas every day?

A

At least 1 litre.

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39
Q

What pH do pancreatic enzymes require so that they can function?

A

A neutral pH.

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40
Q

What part of the intestinal gland cells is responsible for secreting enzymes?

A

The acini.

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41
Q

What part of the intestinal gland cells is responsible for secreting bicarbonate?

A

The ducts.

42
Q

What is the difference in regulation of saliva secretion and pancreatic juice secretion?

A

Saliva = neural regulation.

Pancreatic juice = mainly hormonal regulation and a small amount of neural regulation.

43
Q

What are the 3 major groups of pancreatic enzymes that are produced in the pancreatic acini?

A

Proteolytic enzymes.

Amylolytic enzymes.

Lipolytic enzymes.

44
Q

What is the major amylolytic enzyme that is secreted by the pancreas?

A

Amylase.

45
Q

What is the function of amylase?

A

It splits the alpha 1-4 glycosydic linkage in carbohydrates.

46
Q

What happens to polysaccharides after exposure to amylase?

A

They are broken into oligosaccharides and disaccharides.

47
Q

Will amylase break down complex carbohydrates?

A

No.

48
Q

What is the most common carbohydrate that is broken down by amylase?

A

Starch.

49
Q

What are the 4 proteolytic enzymes secreted by the pancreas?

A

Trypsinogen.

Chymotrypsinogen.

Pro-elastase.

Pro-carboxypeptidases.

50
Q

Proteolytic enzymes secreted from the pancreas in what form?

A

They are secreted as zymogens inside vesicles.

51
Q

Why are proteolytic enzymes stored as zymogens?

A

So they don’t degrade the pancreas.

52
Q

What will activate trypsinogen to form trypsin?

A

Enterokinase.

53
Q

What activates all proteolytic enzymes other than trypsinogen?

A

Trypsin.

54
Q

Why does the pancreas contain a trypsinogen inhibitor?

A

So auto-digestion does not occur.

55
Q

What are 3 common lipases that are produced by the pancreas?

A

Pancreatic lipase.

Pro-phospholipase.

Cholinesterase.

56
Q

How do lipases break down fats?

A

They attach to fat globules and break them down into fatty acids and monoglycerides.

57
Q

What is the difference between pepsinogen and trypsinogen?

A

Pepsinogen is the proteolytic enzyme in the stomach.

Trypsinogen in the proteolytic enzyme in the duodenum.

58
Q

What are the active forms of pepsinogen and trypsinogen?

A

Pepsin and trypsin.

59
Q

What additional factor is also required for the digestion of fats?

A

Bile salts.

60
Q

Will pancreatic enzyme break down nutrients into such a size that they can be absorbed?

A

No.

Enzymes from the mucosa of the small intestine will do this.

61
Q

Is the pancreas stimulated to release enzymes etc during the cephalic or gastric phases?

A

Yes, but it releases very few secretions.

62
Q

What phase of digestion will most of the pancreatic enzymes be secreted in?

A

In the intestinal phase.

63
Q

What part of the pancreas secretes enzymes to the duodenum?

A

The exocrine portion.

64
Q

What are the 2 hormones that lead to the major secretion of pancreatic enzymes?

A

Choleocystokinin.

Secretin.

65
Q

What leads to the release of choleocystokinin?

A

Low pH in the duodenum.

66
Q

What is the function of choleocystokinin?

A

It leads to bicarbonate secretion.

67
Q

What leads to the release of secretin?

A

The presence of fats and proteins in the duodenum.

68
Q

What is the function of secretin?

A

It leads to the release of pancreatic enzymes.

69
Q

What determines how much pancreatic juice is secreted into the duodenum?

A

The amount of acid and nutrients in the chyme.

70
Q

What animals basically have a constant flow of pancreatic juice into the duodenum?

A

Ruminants and horses.

71
Q

How do pancreatic secretions differ in ruminants and horses?

A

Both have constant secretion of pancreatic juices, but horses will increase secretions when food enters the duodenum.

72
Q

How much pancreatic enzymes will be secreted by horses in a day?

A

30-35 L.

73
Q

How much pancreatic enzymes will be secreted by ruminants in a day?

A

4-5 L.

74
Q

Why do horses secrete a lot of pancreatic juices?

A

As they need a lot of bicarbonate as they don’t secrete much saliva.

75
Q

What happens to digestion if there is a problem with the pancreas?

A

There will be incomplete digestion of fats and proteins.

76
Q

What are 2 common pancreatic disorders?

A

Acute pancreatitis.

Exocrine pancreas insufficiency.

77
Q

What can cause acute pancreatitis?

A

Spice food.

Infections.

Trauma.

Fat rich food.

78
Q

What is acute pancreatitis characterised by?

A

Tissue damage.

Activation of trypsinogen to trypsin.

Auto-digestion of the pancreas.

Leakage of enzymes into circulation.

79
Q

What is exocrine pancreas insufficiency characterised by?

A

Reduced or lack of enzyme secretion.

Maldigestion.

Steatorhoea.

80
Q

What causes exocrine pancreas insufficiency?

A

Chronic inflammation.

Autoimmune diseases.

81
Q

What are the digestive functions of the liver?

A

To help with the digestion and absorption of fats.

To neutralise acidic chyme.

82
Q

What is secreted by the liver into the duodenum of the small intestine?

A

Bicarbonate.

Bile salts.

83
Q

What are the 4 functions of the liver that are not directly associated with digestion?

A

Inactivates toxins, hormones and drugs.

It produces plasma proteins.

It produces blood coagulation factors.

It produces cholesterol.

84
Q

Bile juice is stored in what organ?

A

The gall bladder of the liver.

85
Q

What is the composition of bile?

A

97% water.

  1. 7% bile salts.
  2. 2% bilirubin.
  3. 51% fats and inorganic salts.
86
Q

What secretes bile acid into the gall bladder?

A

The hepatocytes.

87
Q

What are the 2 ways that bile acid can be synthesised?

A

De novo synthesis in the cell.

Enterohepatic circulation.

88
Q

What are conjugated bile acids also referred to as?

A

As bile salts.

89
Q

What breaks down bile salts once they have been released?

A

Bacteria in the large intestine.

90
Q

What molecule is necessary for the de-novo synthesis of bile salts?

A

Cholesterol.

91
Q

What are the 2 major functions of bile salts?

A

Emulsification of fats.

Transport of fats.

92
Q

What is the emulsification of fats?

A

When bile salts attach to large fat globules and break them into smaller globules.

93
Q

How do bile salts attach to fat globules?

A

They use their hydrophobic side to attach to fats and this breaks them up into smaller globules.

94
Q

The breakdown of fat globules into smaller globules allows for what?

A

For digestion by lipases.

95
Q

What is formed by fats after they have been broken down by lipases?

A

Mixed micelles which are a mixture of bile salts and fats.

96
Q

Is bile juice released in the cephalic and gastric phases of digestion?

A

Yes, a little bit.

97
Q

What hormone leads to the release of stored bile?

A

Choleocystokinin.

98
Q

What leads to the release of choleocystokinin?

A

Fats and proteins in the duodenum.

99
Q

What happens to bile salts after fat absorption has occurred?

A

95% of bile salts are re-absorbed.

100
Q

What happens when recycled bile salts are bought into the liver?

A

More bile juice is released.

101
Q

When might bile salts increase in blood plasma?

A

When hepatocytes are damaged and cannot take up bile salts from the portal vein.

Physiology. Gastrointestinal Physiology. (6 decks)

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