Gastric secretion

Question 1

Where is the antrum?

Answer 1

The end of the stomach

Question 2

Function of the fundus?

Answer 2

Storage

Question 3

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

Answer 3

Storage
HCL secretion
Pepsinogen secretion
Mucus and Intrinsic factor secretions

Question 4

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

Answer 4

HCL secretion
Pepsinogen secretion
Mucus and Intrinsic factor secretions

Question 5

Why is pepsinogen released not pepsin?

Answer 5

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

Question 6

Function of the antrum?

Answer 6

Grinding and mizxing
Produces gastrin (hormone)

Question 7

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

Answer 7

G Cells in the antrum

Question 8

What does a gastric pit lead to?

Answer 8

Gastric gland:

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

H2CO3 (Carbonic acid)

Question 11

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

Answer 11

Carbonic anhydrase

Question 12

Where does this reaction occur?

Answer 12

In the parietal cells

Question 13

What does carbonc acid separate into?

Answer 13

H+ and bicarbonate (HCO3)

Question 14

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

Answer 14

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

Question 15

HKAptase aka

Answer 15

Proton potassium pump

Question 16

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

Answer 16

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.

Question 17

What does post prandial mean?

Answer 17

After a meal

Question 18

Does gastrin travel in the blood?

Answer 18

Yes, it is endocrine

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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.

Question 21

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

Answer 21

The Potassium Proton pump, which makes stomach more aciidc.

Question 22

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

Answer 22

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.

Question 23

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

Answer 23

Inhibitory.

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

Question 24

How is gastric acid secretion controlled?

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What is the gastric phase of stimulation?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

Where is secretin released from? What does it cause?

Answer 28

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

Question 29

WHy do we need to neuralise contents into duodenum

Answer 29

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

Question 30

What are enterogastrones? What causes them to be released?

Answer 30

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

Question 31

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

Answer 31

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

Question 32

How does Pepsinogen get converted to pepsin?

Answer 32

Through contact with HCl (in low pH)

Question 33

Are pepsins inactivated in neutral pH?

Answer 33

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

Question 34

How is the release of pepsinogen controlled?

Answer 34

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

Question 35

How is gastric mucous produced?

Answer 35

By surface epithelial cells and mucus neck cells

Question 36

WHat does gastric mucous do?

Answer 36

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

Question 37

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

Answer 37

Pernicious anaemia (failure of erythrocyte maturation)

Question 38

\What is intrinsic factor produced by?

Answer 38

Parietal cells