Lecture 3: Helicobacter pylori Flashcards
Describe the regulation of acid secretion in the cephalic phase?
When you think, smell, taste food the vagus nerve innervates the parietal cells to secrete gastric acid
Describe the regulation of acid secretion in the gastric phase?
This phase is when food has entered the stomach
The presence of food stimulates the stretch receptors.
These stretch receptors trigger a long reflex.
The long reflex will stimulate the release of ACh from the vagus nerve. In turn, this stimulates the G cells.
The G cells will secrete gastrin.
Gastrin innervates the parietal cells to secrete gastric acid
Describe the negative feedback loop that regulates acid secretion?
Gastric secretion is increased in the presence of food.
This stimulates the parietal cells to produce gastric acid.
The gastric acid itself inhibits the G cells.
Hence, inhibiting acid secretion
What are the 3 surgical treatments of duodenal ulcers?
Vagotomy: cutting some branches of the vagus nerve
Subtotal gastroectomy: removal of the entire stomach
Antrectomy: removal of the walls of the antrum
What are the 2 medicines used to treat duodenal ulcers?
H2 receptor antagonist e.g. ranitidine
Proton pump inhibitor e.g. omeprazole
Describe how H.pylori can cause duodenal ulcers?
H. pylori infection cluster in the gastric pits of the stomach.
It increases the acid secretion by parietal cells.
This causes an increase in acid entry into the duodenum causes damage to the duodenal mucosa.
If it erroids to the muscularis mucosa layer- it has become a duodenal ulcer
What are the two ways in which H.pylori increase acid secretion?
- Contains urease, which breaks down urea into ammonia and carbon dioxide. It secretes the ammonia into the lumen creating a “cloud” around it, neutralising the pH. Hence, the parietal cells increase secretion of acid in response to a rise in pH.
- Blocks the D cells from secreting somatostatin (which would inhibit the parietal cells). Therefore, it blocks this feedback loop, increasing acid secretion.
How can the H.pylori bacterium be able to survive in the harsh acidity environment of the stomach?
It has a high urease activity.
It breaks down:
Urea + Water -> Ammonia + Carbon dioxide
It secretes the ammonia into its surroundings, creating a cloud of ammonia.
This ammonia neutralises the acid. Hence, allowing it to survive the harsh acidity environment
What is the difference in prevalence of H.pylori infection in the developing/developed countries?
Developing world:
It seems there is an exponential high percent of people get in when they are younger.
After about 10 the percent infected stays level.
Developed world:
Rates in younger generations are reducing due to improvements of living conditions
What is the socio-economic status of H.pylori infection?
Social status (due to differences in living conditions) have a direct impact on the likelihood of H.pylori infection
What is the negative feedback loop in the stomach that prevents the parietal cells from producing too much acid?
Too much acid secretion stimulates the D cells to secrete somatostatin which inhibits the parietal cells
What are the two ways in which H.pylori cause an increase in gastric acid secretion?
H.pylori fills up the gastric pits and pours out ammonia to neutralise the acid- thus causing acid secretion.
It also blocks D cells, preventing them to provide the negative feedback to limit the acid secretion
What is the ideal treatment for H.pylori infection?
2 antibiotics + Proton pump inhibitor
Eradicates the infection in 80% of cases
What does dyspepsia mean>
aka indigestion
Pain in the upper abdomen
What is the outcome of H.pylori infection if atrophy has started to occur?
The outcome is gastric cancer
Describe how H.pylori infection can cause atrophy and what is the outcome?
With the H.pylori infection, it causes inflammation which can destroy the normal cells of the stomach. Causes these cells to become intestinal metaplasia (these new cells are similar to the ones lining the intestines)
These new cells cannot secrete gastric acid therefore the pH begins to rise.
What is gastritis?
Inflammation of the protective lining of the stomach
What is hypochlorhydria?
Medical term for low level of stomach acid
What is atrophic gastritis?
Chronic inflammation of the gastric mucosa leading to the loss of glandular cells and the replacement with intestinal tissue.
What are the stages of the progression for H.pylori infected to dysplasia?
Atrophic gastritis hypochlorhydria means chronic inflammation of the epithelium of the stomach, resulting in low levels of gastric acid
What are some factors that as suppose to be involved in the development of H.pylori infection into dysplasia?
The type of bacterial strain it is
Host genetics
Male gender
Lifestyle factors e.g. smoking and diet
