Regulation And Disorders Of Gastric Secretion

Question 1

What are the contents of gastric juice in the fasting state?

Answer 1

Cations, anions, pepsinogen, lipase, mucus, intrinsic factors

Question 2

What does the body of the stomach secrete?

Answer 2

Mucus, pepsinogen and HCL

Question 3

What does the antrum of the stomach secrete?

Answer 3

Mucus, pepsinogen and gastrin

Question 4

What is trefoil peptide important for?

Answer 4

Protection of stomach wall

Question 5

How is gastric acid made in the stomach lumen?

Answer 5

• HCO3 exchanged for Cl- in the blood
• excess Cl- diffuses out into stomach
• potassium hydrogen ATPase pumps hydrogen ions out into the stomach lumen

Question 6

What are the 5 types of cells in gastric glands?

Answer 6

Surface mucous cells
Mucus neck cells
Parietal cells
ECL cells
Chief cells

Question 7

What do surface mucus cells do?

Answer 7

Secrete mucus, trefoil peptide and bicarbonate

Question 8

What do mucus neck cells do?

Answer 8

Stem cell compartment

Question 9

What do parietal cells secrete?

Answer 9

Acid and intrinsic factor secretion

Question 10

What do ECL cells secrete?

Answer 10

Histamine

Question 11

What do chief cells secrete?

Answer 11

Pepsinogen

Question 12

What is resting juice?

Answer 12

Alkaline plasma (basically)

Question 13

What is the mucus’ function?

Answer 13

Thick and sticky- forms water insoluble gel on epithelial surface

Question 14

What does mucus do (in stomach)?

Answer 14

Increased HCO3 - protects against hydrogen ion secretion

Question 15

What is renin replaced by?

Answer 15

Pepsinogen

Question 16

What does intrinsic factor do?

Answer 16

Helps with absorption of vit B12

Question 17

What is the function of gastric acid?

Answer 17

Kills bacteria, acidic denature of digested food, creates the optimum pH for activation of pepsinogen, promotes the activation of gastric lipase and secretion of pancreatic HCO3

Question 18

What do G cells secrete?

Answer 18

Gastrin

Question 19

What happens in the cephalic phase?

Answer 19

ACh stimulates histamine release from ECL cells and can also act on parietal cells -> HCL secretion

Gastrin stimulates histamine release and can act directly on parietal cells -> HCL secretions

Question 20

What happens when too much acid is produced?

Answer 20

D cells are stimulated and release somatostatin

Question 21

What is somatostatin?

Answer 21

Paracrine factor

Question 22

What happens in the gastric phase?

Answer 22

Stomach distends, peptic concentration and acidity increases

Peptides in food buffer acid and increase pH so somatostatin inhibitition

Question 23

What happens in the intestinal phase?

Answer 23

Balances the secretory activity of the stomach and the digestive and absorbitive capacities of small intestine
High duodenal acidity reflexively inhibits acid secretion

Question 24

What inhibits acid secretion?

Answer 24

Duodenal distension, hypertonic solution, amino acids, fatty acids and monosaccharides

Question 25

What does inhibition of acid secretion in the small intestine depend on?

Answer 25

Composition of chyme, volume of chyme and distension of the duodenum

Question 26

What is HCL secretion regulated by?

Answer 26

Neuronal pathways and duodenal hormones

Question 27

What is the direct pathway of acid secretion?

Answer 27

Acts on parietal cells-> increased Acid secretion

Question 28

What is the indirect pathway of HCL secretion?

Answer 28

Influencing the secretion of gastrin and histamine,which increase acid secretion

Question 29

What stimulates HCL secretion?

Answer 29

Histamines, ACh, gastrin, caffeine, alcohol, NSAIDs, nicotine, helicobacter pylori,

Question 30

Why is pepsinogen secreted?

Answer 30

Inputs of chief cells from the nerve plexus when the [H+] is high

Question 31

What does PGE2 do?

Answer 31

Inhibits parietal cells and stimulate mucus secreting cells

Question 32

What do NSAIDs inhibit?

Answer 32

PGE2

Question 33

How does the mucus layer prevent the auto digestion of the stomach?

Answer 33

Protects from low pH

Question 34

How do the epithelial cells prevent autodigestion of the stomach?

Answer 34

Remove excess H+ via membrane transport systems

Question 35

How are H+ ions prevented from back diffusing?

Answer 35

Tight junctions of epithelial cells

Question 36

How do prostaglandins prevent the autodigestion of the stomach?

Answer 36

Inhibit acid secretion and enhance blood flow

Question 37

What does mucosal blood flow remove?

Answer 37

Excess acid that has diffused across the epithelial layer

Question 38

What do NSAIDs do?

Answer 38

Cause tropical irritation of the gut

Question 39

What does the presence of acid in stomach promote?

Answer 39

NSAID-mediated gastric disorders

Question 40

What are the functions of the GIT?

Answer 40

Storage, secretions, digestion, absorption of nutrients, salts, water, metabolism and elimination of undigested wastes

Question 41

Where can peptic ulcers form?

Answer 41

Oesophagus, stomach and duodenum

Question 42

When do peptic ulcers form?

Answer 42

Where there’s a breakage in the mucosal barrier

Question 43

Where are peptic ulcers particularly common?

Answer 43

Duodenal cap, stomach- junction of antrum and body, distal oesophagus, meckels diverticulum and weight loss surgery

Question 44

What are the causes of peptic ulcers?

Answer 44

Hyperacidity, presence of H pylori, NSAIDs, genetic factors

Question 45

What are the outcomes of acute peptic ulcers?

Answer 45

Severe bleeding, healing with no scarring and chronic peptic ulcers

Question 46

What do acute peptic ulcers develop from?

Answer 46

Areas of corrosive gastritis or acute hypoxia of surface epithelium

Question 47

How does H pylori cause peptic ulcers?

Answer 47

They can permeate the gastric mucosa and cause ulcers

Question 48

What are the virulence factors of H pylori?

Answer 48

- flagella move it closer to the epithelium - produces urease - cytotoxin-associated antigen (CagA) - vacuolating toxin A (VacA)

Question 49

How does urease make H pylori more virulent?

Answer 49

Converts urea to ammonia- buffers gastric acid and produces CO2

Question 50

How does Cytotoxin-associated antigen make H pylori more virulent?

Answer 50

Inserts pathogenicity islands and confers ulcer-forming potential

Question 51

How does vacuolating toxin A make H pylori more virulent?

Answer 51

Alters the trafficking of intracellular proteins in gastric cells

Question 52

What is the most common cause of peptic ulcers?

Answer 52

H pylori

Question 53

What does H pylori do once its in the cells?

Answer 53

Disregulates gastrin secretion

Question 54

What happens when gastrin secretion is disregulated?

Answer 54

Gastrin secretion increases

Question 55

What are the three ways you can diagnose peptic ulcers?

Answer 55

Endoscopy Histological examination and staining of an EGD biopsy Test for H pylori presence

Question 56

What are the tests you can do for the presence of H pylori?

Answer 56

- stool antigen test - evaluate urease activity - urea breath test

Question 57

How do you carry out the urea breath test?

Answer 57

Work out how much CO2 is in urine and how much is in breath by tagging some C-14. There shouldn’t be any C-14 in breath

Question 58

When do you measure CO2 levels when carrying out the urea breath test?

Answer 58

Before and 10-30 mins after

Question 59

What are the complications of a peptic ulcer?

Answer 59

``` Haemorrhage Perforation and penetration Leakage of luminal contents Narrowing of pyloric canal or oesophageal stricture Malignant change ```