The Intestinal Phase of Digestion.

Question 1

When does the intestinal phase of digestion begin?

Answer 1

When acidic chyme arrives in the small intestine.

Question 2

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

Answer 2

So that the duodenum is not overloaded.

Question 3

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

Answer 3

Distension of small intestine.

High acidity.

High nutrient concentration.

Irritation of intestinal mucosa.

Question 4

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

Answer 4

The enterogastric reflux.

Question 5

What hormones are secreted once cyme arrives in the duodenum?

Answer 5

Cholecystokinin.

Secretin.

Question 6

What is the function of secretin?

Answer 6

It reduces gastric secretions.

Question 7

What is the function of choleocystokinin?

Answer 7

It reduces gastric motility.

Question 8

What stimulates the release of secretin?

Answer 8

Low pH in the duodenum.

Question 9

What stimulates the release of choleocystokinin?

Answer 9

Fats and proteins in the duodenum.

Question 10

What is vomiting?

Answer 10

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

Question 11

What processes will initiate vomiting?

Answer 11

Antiperistalsis in the small intestine.

Contraction of the duodenum.

Gastric wall and cardia relax.

Contraction of the abdominal muscles.

Question 12

Vomiting is a reverse of what process?

Answer 12

Swallowing.

Question 13

What centre of the brain controls vomiting?

Answer 13

The vomiting centre.

Question 14

The vomiting centre receives afferent signals from what 4 areas?

Answer 14

Mechano and chemoreceptors in the GI tract.

Viscera that are not in the GI tract.

Extramedullary centres in the brain.

Chemoreceptor trigger zone.

Question 15

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

Answer 15

It is psychogenic so it caused by things like motion.

Question 16

What will stimulate the chemoreceptor trigger zone to induce vomiting?

Answer 16

Drugs and toxins etc.

Question 17

What are 3 major consequences of severe vomiting?

Answer 17

Loss of fluid.

Loss of potassium ions.

Loss of hydrogen ions.

Question 18

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

Answer 18

You get hyovolemia of the blood.

This lowers blood pressure.

This leads to circulatory shock.

Question 19

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

Answer 19

It leads to hypokalemia.

This leads to hyperpolarisation of cell membranes.

This leads to reduced excitability of nerves/muscles.

This causes weakness and hyporeflexia.

Question 20

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

Answer 20

It causes metabolic alkalosis.

This leads to hypoventilation.

Question 21

What animals will not be able to vomit?

Answer 21

Rodents and horses.

Question 22

What are 4 factors that can lead to gastric ulcers?

Answer 22

NSAID treatment.

Stress.

Increased histamine secretion.

Helicobacter pylori.

Question 23

What animals are gastric ulcers common in?

Answer 23

Horses (particularly young horses).

Dogs.

Question 24

What typically causes stomach ulcers?

Answer 24

A defect in the gastric mucosal barrier.

Question 25

What typically causes duodenal ulcers?

Answer 25

An overproduction of stomach acid.

Question 26

What causes non-glandular ulcers in horses?

Answer 26

A defect in the gastric mucosal barrier.

Question 27

What causes glandular ulcers in horses?

Answer 27

An overproduction of stomach acid.

Question 28

Chyme is a mixture of what 3 substances?

Answer 28

Polypeptides/oligopeptides. Large emulsified fat globules. Dietary carbohydrates.

Question 29

Can anything in chyme be absorbed?

Answer 29

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

Question 30

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

Answer 30

Neutralisation of acid. Breakdown of macromolecules into micromolecules.

Question 31

What organs help with the digestion of chyme?

Answer 31

The pancreas. The liver/gall bladder.

Question 32

How does the pancreas help digest chyme?

Answer 32

It provides buffers and digestive enzymes.

Question 33

How does the liver/gall bladder help digest chyme?

Answer 33

It provides buffers and a fat emulsifier.

Question 34

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

Answer 34

It provides buffers, digestive enzymes and absorption mechanisms.

Question 35

What animals do not have a gall bladder?

Answer 35

Horses.

Question 36

What is secreted by the pancreas into the duodenum?

Answer 36

Bicarbonate and digestive enzymes.

Question 37

Why is bicarbonate secreted into the duodenum?

Answer 37

To increase pH.

Question 38

How much bicarbonate is secreted by the pancreas every day?

Answer 38

At least 1 litre.

Question 39

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

Answer 39

A neutral pH.

Question 40

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

Answer 40

The acini.

Question 41

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

Answer 41

The ducts.

Question 42

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

Answer 42

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

Question 43

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

Answer 43

Proteolytic enzymes. Amylolytic enzymes. Lipolytic enzymes.

Question 44

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

Answer 44

Amylase.

Question 45

What is the function of amylase?

Answer 45

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

Question 46

What happens to polysaccharides after exposure to amylase?

Answer 46

They are broken into oligosaccharides and disaccharides.

Question 47

Will amylase break down complex carbohydrates?

Answer 47

No.

Question 48

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

Answer 48

Starch.

Question 49

What are the 4 proteolytic enzymes secreted by the pancreas?

Answer 49

Trypsinogen. Chymotrypsinogen. Pro-elastase. Pro-carboxypeptidases.

Question 50

Proteolytic enzymes secreted from the pancreas in what form?

Answer 50

They are secreted as zymogens inside vesicles.

Question 51

Why are proteolytic enzymes stored as zymogens?

Answer 51

So they don't degrade the pancreas.

Question 52

What will activate trypsinogen to form trypsin?

Answer 52

Enterokinase.

Question 53

What activates all proteolytic enzymes other than trypsinogen?

Answer 53

Trypsin.

Question 54

Why does the pancreas contain a trypsinogen inhibitor?

Answer 54

So auto-digestion does not occur.

Question 55

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

Answer 55

Pancreatic lipase. Pro-phospholipase. Cholinesterase.

Question 56

How do lipases break down fats?

Answer 56

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

Question 57

What is the difference between pepsinogen and trypsinogen?

Answer 57

Pepsinogen is the proteolytic enzyme in the stomach. Trypsinogen in the proteolytic enzyme in the duodenum.

Question 58

What are the active forms of pepsinogen and trypsinogen?

Answer 58

Pepsin and trypsin.

Question 59

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

Answer 59

Bile salts.

Question 60

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

Answer 60

No. Enzymes from the mucosa of the small intestine will do this.

Question 61

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

Answer 61

Yes, but it releases very few secretions.

Question 62

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

Answer 62

In the intestinal phase.

Question 63

What part of the pancreas secretes enzymes to the duodenum?

Answer 63

The exocrine portion.

Question 64

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

Answer 64

Choleocystokinin. Secretin.

Question 65

What leads to the release of choleocystokinin?

Answer 65

Low pH in the duodenum.

Question 66

What is the function of choleocystokinin?

Answer 66

It leads to bicarbonate secretion.

Question 67

What leads to the release of secretin?

Answer 67

The presence of fats and proteins in the duodenum.

Question 68

What is the function of secretin?

Answer 68

It leads to the release of pancreatic enzymes.

Question 69

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

Answer 69

The amount of acid and nutrients in the chyme.

Question 70

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

Answer 70

Ruminants and horses.

Question 71

How do pancreatic secretions differ in ruminants and horses?

Answer 71

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

Question 72

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

Answer 72

30-35 L.

Question 73

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

Answer 73

4-5 L.

Question 74

Why do horses secrete a lot of pancreatic juices?

Answer 74

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

Question 75

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

Answer 75

There will be incomplete digestion of fats and proteins.

Question 76

What are 2 common pancreatic disorders?

Answer 76

Acute pancreatitis. Exocrine pancreas insufficiency.

Question 77

What can cause acute pancreatitis?

Answer 77

Spice food. Infections. Trauma. Fat rich food.

Question 78

What is acute pancreatitis characterised by?

Answer 78

Tissue damage. Activation of trypsinogen to trypsin. Auto-digestion of the pancreas. Leakage of enzymes into circulation.

Question 79

What is exocrine pancreas insufficiency characterised by?

Answer 79

Reduced or lack of enzyme secretion. Maldigestion. Steatorhoea.

Question 80

What causes exocrine pancreas insufficiency?

Answer 80

Chronic inflammation. Autoimmune diseases.

Question 81

What are the digestive functions of the liver?

Answer 81

To help with the digestion and absorption of fats. To neutralise acidic chyme.

Question 82

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

Answer 82

Bicarbonate. Bile salts.

Question 83

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

Answer 83

Inactivates toxins, hormones and drugs. It produces plasma proteins. It produces blood coagulation factors. It produces cholesterol.

Question 84

Bile juice is stored in what organ?

Answer 84

The gall bladder of the liver.

Question 85

What is the composition of bile?

Answer 85

97% water. 0. 7% bile salts. 0. 2% bilirubin. 0. 51% fats and inorganic salts.

Question 86

What secretes bile acid into the gall bladder?

Answer 86

The hepatocytes.

Question 87

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

Answer 87

De novo synthesis in the cell. Enterohepatic circulation.

Question 88

What are conjugated bile acids also referred to as?

Answer 88

As bile salts.

Question 89

What breaks down bile salts once they have been released?

Answer 89

Bacteria in the large intestine.

Question 90

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

Answer 90

Cholesterol.

Question 91

What are the 2 major functions of bile salts?

Answer 91

Emulsification of fats. Transport of fats.

Question 92

What is the emulsification of fats?

Answer 92

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

Question 93

How do bile salts attach to fat globules?

Answer 93

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

Question 94

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

Answer 94

For digestion by lipases.

Question 95

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

Answer 95

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

Question 96

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

Answer 96

Yes, a little bit.

Question 97

What hormone leads to the release of stored bile?

Answer 97

Choleocystokinin.

Question 98

What leads to the release of choleocystokinin?

Answer 98

Fats and proteins in the duodenum.

Question 99

What happens to bile salts after fat absorption has occurred?

Answer 99

95% of bile salts are re-absorbed.

Question 100

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

Answer 100

More bile juice is released.

Question 101

When might bile salts increase in blood plasma?

Answer 101

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