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TAS Gastroenterology > Functions Of The Components Of The GI System > Flashcards

Functions Of The Components Of The GI System Flashcards

1
Q

Where is saliva produced?

A

The salivary glands

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2
Q

What are the names of the salivary glands?

A
  • Sublingual
  • Submandibular
  • Parotid
  • Buccal
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3
Q

What stimulates the production of saliva?

A

Smell, thought, and presence of food

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4
Q

What does saliva contain?

A

Mainly water, but also small quantities of;

  • Amylase
  • Mucus
  • Lysozyme
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5
Q

What is the function of salivary amylase?

A

Converts polysaccharides to maltose

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6
Q

What is the function of salivary mucus?

A

To allow lubrication

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7
Q

What is the function of salivary lysozyme?

A

It lyses certain bacteria

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8
Q

What is the first stage in breakdown of food?

A

Chewing

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9
Q

What is the purpose of the chewing of food?

A

It allows easier passage into the absorption

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10
Q

Does absorption take place in the mouth?

A

Some drugs can be absorbed through the buccal mucosa, but no nutrient absorption takes place

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11
Q

Give an example of a drug that can be absorbed through the buccal mucosa?

A

Midazolam

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12
Q

What happens when a food bolus is moved to the back of the pharynx?

A

The swallowing centre in the cerebral medulla is activated

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13
Q

What is the result of the activation of the swallowing centre?

A

Closure of the vocal cords and epiglottis

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14
Q

Why is the closure of the vocal cords and epiglottis important in swallowing?

A

Faciltates the safe pasage of the bolus into the oesophagus

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15
Q

How is reflux of food particles back into the mouth prevented?

A

Sphincters at the lower and upper end of the oesophagus

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16
Q

What is the ‘normal’ state of the upper oesophageal sphincter?

A

Tonically contracted

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17
Q

What happens when the upper oesophageal sphincter needs to let food through?

A

It relaxes

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18
Q

What controls the upper oesophageal sphincter?

A

Cranial nerves V, IX, and X

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19
Q

What stimulates peristalsis within the oesophagus?

A

Swallowing a food bolus

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20
Q

What is the role of the inhibitory neurones of the oesophagus in swallowing?

A
  • Induce lower oesophageal sphincter relaxation

- Co-ordinate proximal-to-distal peristaltic contraction

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21
Q

What condition is caused by a failure of the lower oesophageal sphincter to relax?

A

Achalasia

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22
Q

How is achalasia treated?

A

Usually needs surgery to divide the muscles at the lower oesophageal sphincter to allow passage of food into the stomach

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23
Q

Can achalasia occur in children?

A

It is rare, but can still occur

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24
Q

Does any digestion or absorption of food take place in the oesophagus?

A

No

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25
Q

What are the functions of the stomach?

A
  • Storage of food
  • Secretion of digestive juices
  • Mixing up the contents of the stomach into chyme
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26
Q

What unique property does the smooth muscle of the stomach wall have?

A

‘Plasticity’

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27
Q

What does the property of ‘plasticity’ allow?

A

In fully grown children and young adults, the stomach can hold 50-1000ml whilst the pressure or tone exerted on the contents remains the same

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28
Q

What gives the stomach the property of ‘plasticity’?

A

The folds of the stomach mucosa, or rugae, stretch out as the stomach becomes fuller

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29
Q

What happens once the stomach becomes fully distended?

A

The person will experience discomfort, and usually this will prompt them to stop eating

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30
Q

What produces contraction of the stomach?

A

The cells in the fundus

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31
Q

How do the cells in the fundus produce contraction of the stomach?

A

They generate slow-wave potentials that move down the length of the stomach at the pylorus

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32
Q

At what rate do the cells in the fundus of the stomach generate slow-wave potentials?

A

3/minute

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33
Q

Describe the pattern of contractions produced by potentials from the fundus of the stomach?

A

Rhythmic

34
Q

What muscles do not contract as a result of the potentials produced by the fundus of the stomach?

A

Circular muscles

35
Q

What happens to the strength of contractions as they travel from fundus to antrum?

A

Increase in strength

36
Q

Why do contractions of the stomach increase in strength from the fundus to the antrum?

A

The muscle layers in the fundus of the stomach are significantly thinner than the antrum

37
Q

What are antral peristaltic contractions responsible for?

A

Mixing of food

38
Q

What happens to stomach contents as the peristaltic wave meets the pylorus?

A

The pylorus opens enough to allow very watery chyme through

39
Q

What happens to thicker chyme when it reaches the pylorus?

A

It is not able to pass through, and so it is propelled backwards against the pylorus and back into the antrum for further mixing

40
Q

What volume of gastric secretions are produced by a well-hydrated typical child?

A

10-20mk/kg per day

41
Q

What does gastric fluid contain?

A

Water and a combination of secretions

42
Q

Where do the secretions forming gastric fluid arise from?

A

The gastric pits

43
Q

What cells are responsible for producing secretions for gastric fluid?

A
  • Mucous neck cells
  • Chief cells
  • Parietal cells
  • G cells
  • Enterochromaffin-like cells
  • D cells
44
Q

What do mucous neck cells secrete?

A
  • Bicarbonate

- Mucus

45
Q

What is the purpose of the secretion of mucus by the stomach?

A

Provides a protective barrier against damage from mechanical trauma from peristalsis, auto digestion, and acid

46
Q

What do chief cells produce?

A

Pepsiogen

47
Q

What is pepsinogen?

A

A precursor of pepsin

48
Q

What is the function of pepsin?

A

Protein digestion to amino acids

49
Q

What do parietal cells produce?

A
  • Hydrochloric acid

- Intrinsic factor

50
Q

What is the function of hydrochloric acid in the stomach?

A
  • Activates pepsinogen to it’s active form, pepsin
  • Helps break down connective tissue fibres within food contents
  • Destroys microorganisms within food
51
Q

What is the function of intrinsic factor in the stomach?

A

Important for absorption of vitamin B12

52
Q

Where is vitamin B12 absorbed?

A

Terminal ileum

53
Q

Where are G cells found?

A

In the pyloric area

54
Q

What do G cells secrete?

A

Gastrin

55
Q

What is gastrin?

A

A hormone

56
Q

What is the role of gastrin?

A

Integral in stimulation of parental and chief cells to produce their enzymes

57
Q

What do enterochromaffin-like cells produce?

A

Histamine

58
Q

What is the role of histamine in the stomach?

A

It stimulates gastric acid secretions by the parietal cells

59
Q

What do D cells produce?

A

Somatostatin

60
Q

What is the function of somatostatin?

A

Inhibition of acid secretion

61
Q

What is the gastric pH at birth?

A

Neutral range (6-8)

62
Q

Why is the gastric pH in the neutral range at birth?

A

Due to the presence of alkaline amniotic fluids within the stomach

63
Q

What happens to the gastric pH within a day of birth?

A

It falls to 1-3

64
Q

Is gastric acidity well maintained in neonates?

A

No

65
Q

What happens to gastric pH following a milk feed in neonates?

A

It is increased towards neutral

66
Q

When does the production of stomach acidity reach adult capacity?

A

Age 3 years

67
Q

Is the stomach involved in absorption?

A

Relatively little, but does absorb a few products of digestion

68
Q

What produces of digestion can be absorbed by the stomach?

A
  • Glucose
  • Simple sugars
  • Amino acids
  • Some fat-soluble substances
69
Q

Give a fat soluble substance that notably can be absorbed by the stomach

A

Ethanol

70
Q

What determines the absorption of some drugs in the stomach?

A

The gastric pH

71
Q

Give an example of a drug that gastric pH affects the absorption of

A

Aspirin

72
Q

How does gastric pH affect the absorption of aspirin?

A

At low pH, aspirin is absorbed almost as rapidly as water, but as the pH of the stomach rises, aspirin is absorbed more slowly

73
Q

What happens to water in the stomach?

A

It moves freely from gastric contents across gastric mucosa into the blood

74
Q

What is the net contribution of the stomach to the absorption of water?

A

Small

75
Q

Why is the net contribution of the stomach to water absorption small?

A

Because water moves just as easily from the blood across the gastric mucosa to the lumen of the stomach

76
Q

When is the absorption of water and alcohol from the stomach be slowed?

A

If the stomach contains foodstuffs and especially fats

77
Q

Why is the absorption of water and alcohol from slowed if the stomach contains foodstuffs, especially fats?

A

Because gastric emptying is delayed by fats, and most water in any situation is absorbed from the small intestine

78
Q

What does the rate of emptying of the stomach depend on?

A

Physical and chemical composition of the meal

79
Q

Do fluids or solids empty the stomach more quickly?

A

Fluids

80
Q

Do carbohydrates or protein empty the stomach more rapidly?

A

Carbohydrates

TAS Gastroenterology (17 decks)

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