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Alimentary System: Physiology SA > Gastric Secreation > Flashcards

Gastric Secreation Flashcards

1
Q

What is the overall function of the fundus and what property allows this

A

Storage

Thin and stretchy

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2
Q

Other than Storage what is the further function of the Body of the stomach

A 
Production of:
Mucus 
HCL 
Pepsinogen 
Intrinsic factor
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3
Q

What produces mucus in the stomach

A

Epithelial cellls and mucus neck cells

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4
Q

How does the mucus in the stomach have a cytoprotective role

A

Mucus produces a high content of bicarbonate which mops up the Acid creating a neutral pH region on stomach lining

So stops acid corrosion of stomach lining
as well pepsin become inactive due to neutral pH so further protect from pepsin digestion on stomach lining

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5
Q

What is the purpose of pepsinogen in the stomach

A

Inactive from of pepsin, to protect the stomach lining from being digested

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6
Q

How does the oesophagus lining differ from the stomach

A

Doesn’t have mucus layer to protect from acidic conditions

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7
Q

What does parietal cells produce

A

HCL

Intrinsic Factor

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8
Q

What produces pepsinogens

A

Chief cells

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9
Q

What is the three type of cells that compose the gastric glands

A

Mucus neck cells
Chief cells
Parietal cells

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10
Q

Why is the production of intrinsic factor the only essential function of the stomach

A

As is the only non compensated function

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11
Q

What is the intrinsic factor required for

A

Vitamin B12 Absorption at the Ileum

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12
Q

What is the functions of the Antrum of the stomach

A

Mixing and Grinding of stomach (due to thick muscle)

Secretion of gastrin hormon e

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13
Q

When is pepsinogen converted to inactive form

A

When HCL production increases therefore lowering pH to below pH 3

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14
Q

What does the production of pepsin further convert

A

Further pepsingen to active form pepsin

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15
Q

How is HCL formed from parietal cells

A

The diffusion of CO2 from the blood combing with water to form carbonic acid which dissociates to hydrogen and bicarbonate

Hydrogen pumped into the stomach lumen in exchange for potassium

Bicarbonate exchanged into the blood in exchange for chloride

Chloride cross parietal cell through chloride channel

The combines with hydrogen in the stomach lumen to form HCL

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16
Q

How does the presence of HCL affect the pH in the stomach

A

Decreases to pH 2

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17
Q

How does the presence of Bicarbonate affect the pH of the blood

A

Slight increase to pH 7.4

18
Q

What catalyses the formation of carbonic acids in the parietal cell (CO2 + H2O)

A

Carbonic anhydrase

19
Q

What are the three hormones that increase HCL secretion in the parietal cells

A

Gastrin
Achetlycholine
Histamine

20
Q

How does Gastrin hormone and acetylcholine increase the production of Acid

A

Gastrin travels in the blood to the stomach and ACH works on chollingeric receptors,

and both binds to G protein couple receptor that increases calcium level
combining to protein kinase allowing hydrogen out of the parietal cell to form HCL

21
Q

What is used in exchange of hydrogen from the protein pump on the parietal cell

A

Potassium is exchanged into the parietal cell

22
Q

How does histamine cause an increase on acid production

A

acts on G protein couple receptor to trigger the production of cAMP that combined with protein kinase C protein pump
releasing hydrogen to outside the parietal cell

23
Q

How does prostaglandin decrease HCL production in parietal cells

A

Couples up to inhibitory GI protein preventing the formation of cAMP therefore reducing the function of protein kinase protein pump, so hydrogen is not exchanged out of parietal cell

24
Q

Gastric secretion is controlled by what three mechanisms

A

Neurocrine (vagus nerve- ACH, local reflex)
Endocrine (gastrin)
paracrine (histamine)

25
Q

What initiated the cephalic phase

A

Before eating; The site, smell and taste of food,

Getting the body ready to eat, by preparing acid production in your stomach

26
Q

What is the first step in the cephalic phase

A

Increases parasympathetic intervention though vagus nerve

27
Q

What is the affect of increased vagus nerve intervention

A

Acts on G cells, releasing hormone Gastrin that acts on parietal cells

as well parasympathetic intervention triggers release of ACH which acts on parietal cells

Both gastrin and ACH then act on ECL cells to release histamine acting on parietal cells

28
Q

What is the importance of producing acid before you start easting

A

So food can be sterilised upon entry

29
Q

what are the three things that occur during gastric phase

A

Distension of stomach triggers Vagal enteric refelxes, releasing ACH onto parietal cells

Proteins in the stomach activate G cells producing gastrin to act on parietal cells

The production of gastrin and ACH then stimulates ECL cells releasing histamine that acts on parietal cells

30
Q

What cells does Gastrin and ACH act upon to release histamine

A

ECL

31
Q

What cells produce Gastrin

A

G cells

32
Q

What triggers the release of Gastrin hormone

A

Proteins in the stomach ad increased vagus nerve activity

33
Q

How do you inhibit cephalic phase

A

Stop eating will decrease vagal activity

34
Q

How does Gastric phase decrease gastrin production

A

Due to negative feedback as pH decreases (due to increase in HCL) triggers decrease in gastrin stimulation

35
Q

What happens in the intestinal phase when acid is present in duodenum

A

When acid is present in the duodenum causes a enterogastric reflex releases secretin hormone

which both decreases gastrin secretion and gastric stimulation of parietal cells

36
Q

What is the function of secretin

A

Stimulates secretion of bicarbonate that indirectly neutralises acid

and inhibits the release of gastrin or HCL from parietal cells

37
Q

What happens in the intestinal phase when fat is present in duodenum

A

triggers the release of gastric inhibitory peptide (GIP)
that reduces gastric secretion
and decreases parietal HCL secretion

38
Q

Name the 3 Enterogastrones

Hormones released from gland cells in duodenal mucosa

A

Secretin
Cholecystokinin
Gastric inhibitory peptide

39
Q

What two things triggers intestinal phase

A

Acid in duodenum

or fat in duodenum

40
Q

What are enterogastrones released in response to

A

Acid, hypertonic soln, monoglycerides and fatty acids in duodenum

41
Q

What are the enterogastrones strategies to reduce gastric emptying

A

Inhibit motility

or contract pyloric spinchter

42
Q

What is the overall functions of enterogastrogens

A

reduce gastric emptying time

Inhibit gastric secretion

Alimentary System: Physiology SA (9 decks)

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