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Hugh's MD1 Abdominal > GIT Physiology > Flashcards

GIT Physiology Flashcards

1
Q

What type of amylase is the salivary one?

A

alpha-amylase

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1
Q

Where does pepsin act on its target molecule?

A

It hydrolyses the bound between a aromatic aa and a second aa

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1
Q

What is emulsifying?

A

Breaking up fats into droplets

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2
Q

What is vitamin C also known as?

A

L-Ascorbic acid

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3
Q

What is the function of Gastrin releasing peptide?

A

Acts in parallel with ACh from vagus to stimulate gastrin release from G cells

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4
Q

What is the effect of the release of secretin stimulated bicarbonate solution from the pancreas?

A

Neutralised acid and pepsin activity

This leads to reduced stimulation of stomatostatin release from duodenal D cells and stops the vago-vagal and duodenal-pyloric-antral reflexes inhibiting gastric emptying

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4
Q

What type of cells can sense sweet taste?

A

L cells

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4
Q

What type of cells express olfactory receptors?

A

EC cells

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4
Q

Why don’t most things taste good without fats?

A

Most odourants/favour molecules are fat soluble

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4
Q

If tri or dipeptides are absorbed in to the enterocytes what must happen to them?

A

Cleaves into single aa’s by small peptidases

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4
Q

How many transport systems are there for free aa’s?

A

7

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5
Q

What is the function of mucus and bicarbonate release in the duodenum?

A

Create a barrier to gastric acid

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5
Q

What is the result of L cells sensing sweetness?

A

Increased glucose absorption

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5
Q

To what level are proteins digested before they can be absorbed?

A

Tri-, Di-peptides and single aa’s

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6
Q

What does colon fermentation produce?

A

Short chain fatty acids

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7
Q

How is cholesterol esterase activated?

A

By bile

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8
Q

What is the function of Ghrelin?

A

It is released from the stomach in fasted state to increase appetite

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9
Q

Which enzyme is important for breaking cell-cell adhesion?

A

Pepsin

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10
Q

5 of the amino acid absorption systems require what for co-transport?

A

Na - similar to sodium-dependent glucose transporters (SGLT1)

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11
Q

If you don’t have a stomach what supplement do you require?

A

Intrinsic factor

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12
Q

Which cell secrete pepsinogen?

A

Chief cells

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13
Q

Do gastric lipases play a major role in lipid digestion?

A

No

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14
Q

What does the vagovagal reflex pathway control/regulate?

A

Swallowing

Acid secretion

Smooth muscle contraction in stomach and duodenum

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15
Q

What is the product of fibre fermentation?

A

Short chain fatty acids

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16
Q

What neural pathway activates the cephalic phase?

A

The vagus nerve

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17
Q

What are the basic functions of the GIT?

A

Digest food

Absorb nutrients

Excrete waste

Prevention of invasion by pathogens

Contain the microbiome

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17
Q

Where are the major sites of digestion?

A

Duodenum and upper jejunum

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19
Q

What is the last to empty from the stomach? What are the implications?

A

Fat

Massive increase in CCK release when it come through

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20
Q

Which enzyme digests sucrose? What are the products of its digestion?

A

Sucrase

Glucose and fructose

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20
Q

Which enzyme activates enzymes from the pancreatic juices?

A

Enterokinase

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21
Q

What is the name of the enzyme that digests sugars?

A

Amylase

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22
Q

What does the endocrine control system regulate?

A

Secretion of enzymes and solvents into the intestinal lumen

Helps regulate appetite

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23
Q

What are two disaccharides human digested commonly?

A

Lactose and sucrose

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23
Q

What enzymes cleave at the amino end of peptide chains?

A

Aminopeptidases

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24
Q

What is the major transporter for glucose absorption?

A

Sodium-dependent glucose transporter - Na provides the energy

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25
Q

Which hormone’s release is stimulated by tastants?

A

Serotonin (EC cells)

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25
Q

Where is conscious control required in the defecation process?

A

Relaxation of anal sphincter

Contraction of abdominal muscles

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25
Q

Does the salivary amylase make it through the stomach?

A

Yes and it is reactivated once the pH returns to neutral

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25
Q

What are micelles composed of?

A

Bile salts with lecithin and monoglycerides

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26
Q

How are fats absorbed into the epithelium?

A

Micelles come into contact with lipid membrane and lipids dissolve and enter cells

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28
Q

What do enterochromaffin cell-like cell release?

A

Histamine

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30
Q

What three factors stimulate gastric acid secretion in parietal cells?

A

Vagus stimulation via enteric nerves releasing ACh acting on parietal cells

Histamine for enterochromaffin cell-like cell

Gastrin from G cells in the antrum (of stomach) and duodenum (endocrine signalling - must travel through the portal system)

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31
Q

What does cholesterol esterase do?

A

Hydrolyse cholesterol esters and esters of fat soluble vitamins and phospholipids

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32
Q

What happens to fat in the stomach?

A

It floats to the top due to action of acid, pepsin and mechanical action

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33
Q

What happens if the lower oesophageal sphincter doesn’t close properly?

A

Oesophageal reflux

If chronic - can lead to GORD - gastrooesophageal reflux disease

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34
Q

What happens to fatty acids and monoglycerides inside epithelials cells?

A

They form triglycerides in the smooth endoplasmic reticulum

35
Q

How does somatostatin act on parietal cells?

A

By paracrine action directly on parietal cells to dampen acid secretion and,

By inhibiting histamine (which stimulates parietal cell acid secretion) release in enterochromaffin cell-like cells

37
Q

What mechanism of sensing are present in the intestine lumen?

A

Mechanical reception - distension and mucosal deformation

Chemical stimuli

37
Q

What type of vessel do chylomicrons get exocytosed into for enterocytes?

A

Lymphatics

39
Q

What happens when the GIT is activated during the cephalic stage of eating?

A

Salivation begins

Gastric acid pepsin secretion begins

The gastric body and fundus relax

41
Q

What four functions must be regulated in the GIT?

A

Contractions of muscles to mix food

Secretion of digestive enzymes

Re-absorption of water

Coordination of separate regions

43
Q

When food initially enters the duodenum, what is the fat content?

A

Low

44
Q

What linkage can’t pancreatic and salivary amylase digest?

A

1:6alpha

45
Q

What does the CNS control in relation to food?

A

Anticipation

Mood/activity - fight or flight responses

46
Q

Does glucose and fructose require digestion in the GIT?

A

No, they are immediately absorbed

47
Q

Triglycerides are covered by what to form chylomicrons?

A

Apolipoproteins

48
Q

Where do aa go after being absorbed into enterocytes?

A

Blood > portal circulation > liver

49
Q

Which enzyme acts at the carboxy end of polypeptides?

A

Pancreatic carboxypeptidases

50
Q

Which transporter facilitates fructose transport into the epithelium?

A

GLUT5

52
Q

What is the consistency of the food when it leaves the antrum?

A

Diluted paste

53
Q

What enzymes digest maltotriose and maltose?

A

Isomaltase

Sucrose

Maltase

54
Q

Which endocrine signal induces expression of alpha-amylase in the pancreas?

A

CCK

56
Q

What is segmentation?

A

A motor pattern in the duodenum where there are alternate contrictions and relaxations to further mix food with digestive enzymes and bile and bring it into contact with the epithelium for absorption

57
Q

Via what pathway does acid trigger the release of mucus and bicarbonate by Brunner’s cells?

A

Vagal afferent neurones trigger the vago-vagal reflex

58
Q

What stimulates the urge to defecate?

A

Distension of the rectum

59
Q

What is sacrose a polymer of?

A

Glucose and fructose

60
Q

Distension of the stomach causes what?

A

Activation of enteric and vago-vagal reflexes that lead to more acid and pepsin release

61
Q

What is fermented in the distal small intestine and colon?

A

Cellulose

62
Q

How is it insured that pancreatic enzymes are only active once they reach the food?

A

With a multi-dependent activation cascade.

63
Q

Why must pepsin have an inactivated form?

A

So it doesn’t digest the contents of the cells it’s stored in

64
Q

Which sugar polymers are digested at the brush boarder?

A

Oligosaccharides

Disaccharides

65
Q

Why must D cells in the duodenum release much greater amounts of somatostatin cf to those in the stomach for it to have it desired effect?

A

It must travel through the portal system and the whole body therefore it is diluted

67
Q

At what point does the microbiota metabolism start?

A

Ileum and colon

67
Q

What linkage does alpha-amylase hydrolyse?

A

1:4alpha

68
Q

How does activation of sweet taste receptors increase glucose absorption?

A

It activates glucose-Na channels

70
Q

Where is primary peristalsis generated from? How is it communicated to the GIT?

A

The brain

Vagus nerve

71
Q

Why might initial acid digestion in the mouth be important?

A

Initiates preparation of lipid storage

73
Q

Which enzyme can break I:6alpha linkages?

A

Isomaltase

74
Q

What are the name of the intrinsic pacemaker cells in the muscles?

A

Interstitial cells of Cajal

74
Q

Does fat digestion occur in the mouth?

A

Yes, starts with lingual lipase

75
Q

What is the first thing that must happen when food enters the duodenum?

A

Neutralise acids

77
Q

What does cholecystokinin excite? What is the effects? (there are three)

A

Afferent vagal nerves that act on the hypothalamus to suppress appetite

Enteric sensory neurones to activate motor action to mix food

Contraction of gall bladder for secretion and pancreatic digestive enzymes secretion

79
Q

What is the function of the neurally regulated interdigestive motor complex?

A

Clear bacteria to prevent overgrowth

80
Q

Amino acids and fatty acids stimulate release of what from which cells?

A

CCK (cholecystokinin) from I cells

Secretin from S cells (just AA’s)

81
Q

T/F the majority of movement in the intestines after a meal is propulsion?

A

False, 90% is mixing

82
Q

What is retropulsion?

A

Food pushed back towards pyloris to facilitate mixing with pancreatic duct secretions and bile - further digestion

83
Q

Which transporter facilitate fructose transport from the epithelium to the interstitium?

A

GLUT2

84
Q

What is the function of secretin?

A

Stimulate secretion of a bicarbonate solution from the pancreas

85
Q

How is lipase activated?

A

Colipase activates it

Colipase is activated by trypsin

87
Q

What does the enteric nervous system and institial cells of Cajal regulate?

A

Contractile activity and secretion of water and salt

88
Q

Why do enteroendocrine cells often span the epithelium?

A

So they can release mediators into the lumen of the GIT or into the blood stream

89
Q

Which endocrine hormone is required for secretion of pancreatic lipolytic enzymes?

A

CCK

91
Q

What are the 4 responses to acid in the duodenum?

A

Activates D cells to release somatostatin

Activates to Brunner’s glands produce mucus and bicarbonate

Activates the vago-vagal reflex to stop gastric emptying

Duodenal-pyloro-antral reflex closes the pylorus to further prevent gastric emptying

92
Q

Which is absorbed better, glucose or fructose?

A

Glucose

93
Q

Are enzymes released in the pancreas active?

A

No, they’re in their inactivated form

94
Q

Where do trypsin, elastase and chymotrypsins act on their substrates (it’s the same for each of them)?

A

At the interior bonds of peptides to produce short polypeptides

95
Q

Where is pepsinogen I secreted?

A

Acid secreting region of the stomach

97
Q

T/F Smooth muscle cells of the GIT have intrinsic pacemakers

A

True

99
Q

How do active maltase and sucrase get to their site of action?

A

An inactivated pro form is placed on the mucosal membrane as combined glycoprotein until pancreatic proteases cleave them to activate them

100
Q

What does digestion by pancreatic carboxypeptidases produce?

A

single aa’s

101
Q

Where is pepsinogen II secreted?

A

Pylorus

102
Q

What does the body and antrum of the stomach do before food enters?

A

Reflex to accommodate

103
Q

T/F Cellulose and starch are resistant to digestion.

A

False, only cellulose

104
Q

What emulsifies lipids in the GIT?

A

Bile salt and lecithin

105
Q

What is the cephalic stage of eating?

A

The sight and smell of food initates aspects of the GIT including salivation. The site of food will affect how it tastes eg red lollies taste “sweeter”

106
Q

What does pepsinogen become?

A

Pepsin

107
Q

What activates pepsinogen secretion by chief cells?

A

Gastrin

108
Q

What controls swallowing?

A

Somatic NS via vagus

109
Q

Where is CCK released in sugar digestion?

A

Duodenal mucosa

110
Q

What stimulates D cells to release somatostatin?

A

Vagal stimulation via the enteric ns releasing ACh

Gastrin released from G cells

Acid in the stomach

111
Q

What is the response to food entering the fundus?

A

Inhibition of acid secretion in the body

112
Q

How are short chain fatty acids absorbed?

A

In a H+ dependent manner in the distal small intestine and colon

113
Q

What factor tones down gastric acid secretion by parietal cells? Which cells release it?

A

Somatostatin

D cells

114
Q

What are enteroendocrine cells?

A

GIT signally cells that contain many different hormone signalling molecules

Hugh's MD1 Abdominal (21 decks)

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