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Ailimentary 2 > Gastric secretion > Flashcards

Gastric secretion Flashcards

1
Q

Where is the antrum?

A

The end of the stomach

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2
Q

Function of the fundus?

A

Storage

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3
Q

Function of the body of the stomach? What 4 things does it secrete?

A

Storage
HCL secretion
Pepsinogen secretion
Mucus and Intrinsic factor secretions

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4
Q

Wht does the body of the stomach produce?HCL secretion
Pepsinogen secretion
Mucus and Intrinsic factor secretions

A

HCL secretion
Pepsinogen secretion
Mucus and Intrinsic factor secretions

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5
Q

Why is pepsinogen released not pepsin?

A

Because pepsin would degrade the stomach and we wouldn’t have one :(

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6
Q

Function of the antrum?

A

Grinding and mizxing
Produces gastrin (hormone)

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7
Q

What cells and where is gastrin released? (a hormone)

A

G Cells in the antrum

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8
Q

What does a gastric pit lead to?

A

Gastric gland:

-Mucus neck - become/replace the mucus cells in the epithelium (mucus)
-Parietal cells (HCL and intrinsic factor)
-Chief cells (Pepsinogen)

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9
Q

What cells are in a gastric pit and what do they produce?

A

-Mucus neck - become/replace the mucus cells in the epithelium (mucus)
-Parietal cells (HCL and intrinsic factor)
-Chief cells (Pepsinogen)

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10
Q

What do CO2 and H2O combine to form (in parietal cells)?

A

H2CO3 (Carbonic acid)

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11
Q

What enzyme speeds up this reaction? (CO2 +H20)

A

Carbonic anhydrase

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12
Q

Where does this reaction occur?

A

In the parietal cells

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13
Q

What does carbonc acid separate into?

A

H+ and bicarbonate (HCO3)

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14
Q

How do the hydrogen ions leave the cell into the stomach?

A

Through the HK ATPase pump into the lumen of the stomach though the apical membrane

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15
Q

HKAptase aka

A

Proton potassium pump

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16
Q

Bicarbondate goes wehere/ How? What happens to blood pH after a meal? Ho w does Cl get into stomach lumen?

A

Bicarbonate goes into the blood through the basolateral membrane (Bicarbonate Chloride pump).

Blood pH increases slightluy because more bicarbonate being pumped into the blood

Cl enters through the bicarbonate/Chloride pump.

17
Q

What does post prandial mean?

A

After a meal

18
Q

Does gastrin travel in the blood?

A

Yes, it is endocrine

19
Q

What happens when gastrin attaches to receptor on basolateral membrane of parietal cell?

A

Stimulates influx of Ca, stimulates protein kinases which increases the activity of the HKATPase pump, leading to more H in Stomach

20
Q

H2Histamine receptor is where? Coupled up to what? Converts what to what? Which works on what and causes what?

A

On the basolateral membrane of the parietal cells, coupled with G protein (Gs - G Stimulatary) - Activates AC (Air conditioning jks - Adenylate cyclase). In turn ATP - cAMP. cAMP activates proteikn kinase A - stimulates HKATPase pump. More acidic stomach.

21
Q

So Gastrin, histamine and ACh (Acytyl Choline) are stimulatory to which ATPase and so then what?

A

The Potassium Proton pump, which makes stomach more aciidc.

22
Q

ACH released when? Acts on what? Acts on what?

A

By stimulation of the parasympathetic nervous system. Acts on M3 (muscarinic recpetor), also leads to an influx of Ca, activates protein kinases and stimulates HKATPase pump.

23
Q

Wht effect do Prostaglandins do? Essentially inhibitory or stimulatory of the proton pump?

A

Inhibitory.

Protoglandin - receptor - Gi (G inhibitory protein), inhibit Air Conditioning (AC) and therefore the HKATPase pump

24
Q

How is gastric acid secretion controlled?

A

Endocrine (release of gastrin)
Vagal and local reflexes - parasympathetic
Paracrine - histamine

25
Q

What is the Cephalic phase of stimulation of gastric acid secretion? How does it innervate?

A

Sight, smell, taste of food -> stimlation of vagus nerve (parasympathetic rest and digest):
-> ACh release
-> stimulation of G cells to release Gastrin

ACh and Gastrin stimulate ECL releasing Histamine

Gastrin, Histamine and ACh act on the Parietal cells to get HCl into the stomach

26
Q

What is the gastric phase of stimulation?

A

Presence of food in the lower oesophageal sphincter -> stimulates vagus nerve and enteric reflexes -> ACh

Protein in stomach -> stimulates the relase of gastrin (G Cells)

Gastrin and Histamine both stimulate ECL to relase histamine whihc also acts on Parietal cells

27
Q

What are the mechanisms inhibiting gastric acid secretion? (Cephalic, Gastric and Intestinal and fat/carbs)

A

Cephalic - stop eating/thinking/smelling food - reduced vagal activity

Gastrin - negative feedback. Gastrin casues HCl release, as pH drops, there is a reduced gastrin release

Intestinal Phase - Duodenum acid initiates enterogstric (splanchnic reflex). Also sectrets secretin (S Cells in duodenum mucosa, creates bicarbonate secretion which neutralises acid)

Fat/CHO in Duodenum -> GIP (Gastrin Inhibitory Peptide) -> reduced gastrin secretion and reduced parietal HCl secretion

28
Q

Where is secretin released from? What does it cause?

A

S cells in duodenum mucosa in response to acid. Causes bicarbonate release which in turn neutralises acid.

29
Q

WHy do we need to neuralise contents into duodenum

A

Because otherwise it will denature the enzymes used in digestion. Also will damage the duodenal surface

30
Q

What are enterogastrones? What causes them to be released?

A

Hormones released from the glad cells in the duodenal mucosa:
-secretin
-Cholecystokinin (CKK)
-GIP

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

31
Q

Which 2 ways do enterogastrones prevent further acid build up in the duodenum?

A

Inhibit gastric acid secretion
Reduce gsatric emptying (inhibit motility/contract pyloric sphincter)

32
Q

How does Pepsinogen get converted to pepsin?

A

Through contact with HCl (in low pH)

33
Q

Are pepsins inactivated in neutral pH?

A

Yes (phew! Otherwise they would digest our intestines!)

34
Q

How is the release of pepsinogen controlled?

A

Control of Chief cells which is the same as for the parietal cells and releae of HCl;

35
Q

How is gastric mucous produced?

A

By surface epithelial cells and mucus neck cells

36
Q

WHat does gastric mucous do?

A

Lubricates and protects!

Protects mucosal surface from mechanical injury and maintains neutral pH (high HCO3 content) preventing corrosion and pepsin digestion

37
Q

What do we get if don’t absrob vit B12?

A

Pernicious anaemia (failure of erythrocyte maturation)

38
Q

\What is intrinsic factor produced by?

A

Parietal cells

Ailimentary 2 (9 decks)

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