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Alimentary System > Gastric Secretion > Flashcards

Gastric Secretion Flashcards

1
Q

What are the three main functional parts of the stomach?

A

Fundus, body and antrum

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2
Q

What is the fundus of the stomach responsible for?

A

Storage

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3
Q

What are the functions of the body of the stomach?

A 
Storage 
Mucous production 
HCl production 
Pepsinogen production 
Production of intrinsic factor
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4
Q

What are the functions of the antrum of the stomach?

A

Mixing and grinding of the stomach contents

Production of gastrin

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5
Q

What feature of the antrum aids the mixing and grinding of the stomach contents?

A

Very thick muscularis externae

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6
Q

Where is gastrin released and what does it do?

A

Released in the antrum, gastro-intestinal hormone which is secreted into stomach lumen, taken into circulation then returned to stimulate the stomach cells

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7
Q

What three mechanisms control gastric acid secretion?

A

Neurocrine - vagus nerve and local reflexes
Endocrine - gastrin
Paracrine - histamine

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8
Q

What is the first thing to prepare the stomach for digestion and what does this cause?

A

Precursors to eating - sight, smell and taste of food

Causes stomach to create acid which will instantly sterilise any bacteria ingested

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9
Q

What three things are stimulated by the vagus nerve or by gastrin in the cephalic phase to trigger acid production?

A

Stomach
G cells
ECL cells

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10
Q

When does the gastric phase occur?

A

Once there is a physical presence of food in the stomach

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11
Q

Distension of the stomach (gastric phase) triggers long reflexes from the _ and short reflexes from the _

A

Vagus nerve

Enteric reflexes

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12
Q

Vagus nerve and enteric reflexes trigger the release of

A

ACh

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13
Q

Peptides in the lumen stimulate

A

G cells which release gastrin

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14
Q

Gastrin and ACh can also stimulate the ECL cells which release

A

histamine

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15
Q

What will inhibit gastric acid secretion in the cephalic phase?

A

Absence of stimulus i.e. stop eating

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16
Q

What will inhibit gastric acid secretion in the gastric phase?

A

H ion increases, pH decreases leading to decreased gastrin release as environment is acidic enough

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17
Q

Pancreatic enzymes are extremely sensitive to

A

acid/low pH

18
Q

Acid in the duodenum triggers

A

the enterogastric reflex and secretin release from the surface of the duodenum

19
Q

Secretin triggers the release of

A

bicarbonate

20
Q

Secretin and bicarbonate will cause

A

reduction in gastric secretion and therefore reduce the effect of gastrin stimulation on the parietal cells

21
Q

Fat in the duodenum causes the release of _ which causes

A

gastric inhibitory peptide

causes reduced gastric secretion and reduced parietal HCl secretion

22
Q

The intestinal phase occurs when

A

signals are sent that the stomach is emptying its contents

23
Q

The intestinal phase reduces

A

acid damage to the duodenum

24
Q

What is pepsinogen?

A

The zymogen of pepsin

25
Q

What is a zymogen?

A

An inactive precursor of an enzyme

26
Q

When is pepsinogen converted to pepsin?

A

When the pH is below 3

27
Q

When are pepsins inactivated?

A

At neutral pH

28
Q

Gastric motility causes the

A

mixing of the stomach contents, contraction of pyloric sphincter and further mixing

29
Q

What is the function of the pyloric sphincter?

A

Controls passage of stomach contents into the duodenum

30
Q

What are responsible for gastric motility?

A

Peristaltic waves

31
Q

Where do peristaltic waves originate?

A

Oesophagus

32
Q

Why are more powerful contractions possible once the peristaltic wave reaches the antrum and pyloric sphincter?

A

As the muscle here is thicker and more powerful

33
Q

Does gastrin increase or decrease contraction in the stomach?

A

Increase

34
Q

How is the stomach emptied?

A

Gradually

35
Q

The presence of what in the duodenum will inhibit gastric motility?

A

Fat
Acid
Amino acids
Hypertonicity

36
Q

What is the only essential, non-compensated function of the stomach?

A

Releasing intrinsic factor to form a complex with vitamin B12, allowing it to be absorbed from the ileum

37
Q

What will a defect in intrinsic factor lead to?

A

Pernicious anaemia

38
Q

What cells produce gastric mucous?

A

Surface epithelial cells and mucous neck cells

39
Q

What role does gastric mucous have?

A

Cytoprotective role

40
Q

What is the function of the high bicarbonate content of gastric mucous?

A

Neutralises the pH of gastric acid, completely denaturing pepsin and stopping the corrosive acid from reaching the cells below the mucous layer

Alimentary System (29 decks)

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