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Systems: Alimentary AB > Gastric Secretion > Flashcards

Gastric Secretion Flashcards

1
Q

What is the function of the fundus of the stomach?

A

Storage

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2
Q

What are the functions of the body of the stomach?

A
  • Storage
  • Addition of mucus
  • Addition of HCL
  • Activation of pepsinogen
  • Addition of intrinsic factor
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3
Q

What is the function of the antrum of the stomach?

A
  • Mixing/grinding

- Gastrin

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4
Q

What do the mucous neck cells secrete?

A

Mucus

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5
Q

What do the chief cells secrete?

A

Pepsinogens

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6
Q

What do the parietal cells secrete?

A
  • HCL

- Intrinsic factor

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7
Q

What is the pH of the lumen of the stomach?

A

<2

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8
Q

What is the pH of the blood?

A

7.4

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9
Q

What does carbonic anhydrase catalyse?

A

Reaction of CO2 to carbonic acid

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10
Q

Describe the movement of ions between the blood, and stomach lumen.

A
  • CO2 from the blood combines with H20 to form carbonic acid.
  • Hydrogen from the carbonic acid is pumped out of the cell as potassium is pumped into the cell.
  • Bicarbonate remains which is pumped into the blood as Cl is pumped into the cell.
  • The Cl then moves into the lumen of the stomach
  • Water passes from blood to stomach lumen paracellularly
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11
Q

Slide 5

A

Slide 5

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12
Q

What are the 3 mechanisms which control gastric acid secretion?

A
  • Neuroncrine
  • Endocrine
  • Paracrine
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13
Q

How is neurocrine control of gastric acid secretion achieved?

A

Via vagus and local reflexes

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14
Q

How is endocrine control of gastric acid secretion achieved?

A

Via gastrin

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15
Q

How is paracrine control of gastric acid secretion achieved?

A

Via histamine

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16
Q

Describe the cephalic phase of gastric acid secretion.

A
  • Sight, smell and taste of food increases action of Vagus nerve.
  • Produces an increase in ACh which acts on parietal cells.
  • Vagus activate G cells which increase gastrin release which acts on parietal cells
  • Gastrin and ACh act on ECL cells which increase release of histamine which act on parietal cells
17
Q

Describe the 3 parts of the gastric phase of gastric acid secretion.

A
  • Arrival of food produces distension of stomach. Produces vagal and enteric reflexes releasing ACh acting on parietal cells
  • Peptides in lumen activate G cells which release gastrin acting on parietal cells
  • Gastrin/ACh act on ECL cells which release histamine acting on parietal cells
18
Q

How is gastric acid secretion inhibited at the cephalic stage?

A

Stopping eating decreases vagal activity

19
Q

How is gastric acid secretion inhibited at the gastric phase?

A

Decrease in pH as a result of an increase in HCl leads to a decrease in gastrin

20
Q

How does acid in the duodenum inhibit gastric acid secretion at the intestinal phase?

A

-Produces enterogastric reflex and secretin release which both lower gastrin secretion and gastrin stimulation of parietal cells

21
Q

How does fat in the duodenum inhibit gastric acid secretion at the intestinal phase?

A

Leads to GIP release which decreases gastrin secretion and parietal HCl secretion

22
Q

What are enterogastrones?

A

Hormones released from gland cells in duodenal mucosa

23
Q

Give 3 examples of enterogastrones.

A
  • Secretin
  • Cholecystokinin
  • GIP
24
Q

When are enterogastrones released?

A

In response to acid, hypertonic solutions, fatty acids or monoglycerides in duodenum

25
Q

What do enterogastrones do?

A

Act collectively to prevent further acid build up in duodenum

26
Q

What are the 2 strategies used by enterogastrones?

A
  • Inhibit gastric acid secretion

- Reduce gastric emptying (inhibit motility/contract pyloric sphincter)

27
Q

What secretes pepsinogen?

A

Chief cells

28
Q

When is pepsinogen converted to pepsin?

A

Low pH <3

29
Q

Zymogen

A

Inactive precursor

30
Q

What does zymogen storage prevent?

A

Cellular digestion

31
Q

When are pepsins inactivated?

A

At neutral pH

32
Q

What are mechanisms for pepsin control of pepsin secretion parallel to?

A

Mechanisms for HCl secretion

33
Q

Where is gastric mucus produced

A

Produced by surface epithelial cells and mucus neck cells

34
Q

Describe the cytoprotective role of gastric mucus.

A

-Protects mucosal surface from mechanical injury

Neutral pH protects against gastric acid corrosion and pepsin digestion

35
Q

What is the only essential function of the stomach?

A

Secretion of intrinsic factor

36
Q

What produces intrinsic factor?

A

Parietal cells

37
Q

What is intrinsic factor required for?

A

Vitamin B12 absorption

38
Q

Where is the intrinsic factor/B12 complex absorbed?

A

Ileum

39
Q

What can failure of intrinsic factor lead to?

A

Pernicious anaemia which is failure of erythrocyte maturation

Systems: Alimentary AB (37 decks)

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