S5 Functions Of The Stomach

Question 1

What are the 3 main functions of the stomach?

Answer 1

Store and disrupt food
Disinfect food
Activate proteases

Question 2

Describe the different parts of the stomach

Answer 2

At the entrance is the cardia
Fundus is at the top
Below is the body
Antrum is near the pyloric sphincter

Question 3

What are the functions of the upper and lower areas of the stomach?

Answer 3

Upper stomach: has regular sustained contractions creating a basal tone of flow down the tube to reduce reflux
Lower stomach: strong peristalsis mixes stomach contents, coordinated movements

Question 4

What is receptive relaxation?

Answer 4

Vagally mediated relaxation of the orad stomach (fundus + top ½ of the body), allowing storage of food since we consume faster than we digest.

Question 5

Which cells secrete which substance in the stomach?

Answer 5

Parietal - HCL and intrinsic factor 
G cell - gastrin 
Enterochromaffin like cells - histamine 
Chief cell - pepsinogen 
D cell - somatostatin 
Mucus cell - mucus

Question 6

Which cells are found mainly in the cardia, fundus and pylorus?

Answer 6

Cardia- mucus
Fundus and body - mucus, HCl, pepsinogen
Pylorus - gastrin, somatostatin

Question 7

How does gastrin cause HCL secretion?

Answer 7

Gastrin acts on CCK receptor on parietal cell which causes HCL secretion

Question 8

How does histamine cause HCL secretion?

Answer 8

Enterochromafin cells release histamine which acts on H2 receptor on parietal cell causing HCL secretion.

Question 9

How does ACh cause HCL secretion?

Answer 9

Vagus nerve releases ACh which binds to muscarinic receptor on parietal cell causing HCL secretion

Question 10

How is gastrin secretion controlled?

Answer 10

G cells in antrum stimulated by peptides and vagal stimulation (ACh and GRP).
Inhibition is via somatostatin.

Question 11

What happens in the cephalic phase of digestion?

Answer 11

Parasympathetic stimulation from chewing cause’s direct stimulation of parietal cell by vagus nerve, and stimulation of G cells by vagus nerve

Question 12

What happens in the gastric phase of digestion?

Answer 12

Distension of stomach and presence of amino acids stimulates G cells and parietal cells

Question 13

What happens in the intestinal phase of digestion?

Answer 13

Chyme stimulates CCK and secretin which help suppress secretion of gastrin.

Question 14

How does the stomach epithelia protect itself?

Answer 14

Mucus forms an alkaline layer protecting the epithelia
High turnover of epithelial cells
Prostaglandins maintain mucosal blood flow to epithelium

Question 15

What is GORD?

Answer 15

Excess reflux of stomach contents into oesophagus

Question 16

What are the causes of GORD?

Answer 16

Issues with lower oesophageal sphincter

Obesity

Question 17

What are the symptoms and complications of GORD?

Answer 17

Heartburn, sore throat, dysphasia

Barrett’s oesophagus

Question 18

What is acute gastritis?

Answer 18

Acute mucosal inflammation

Can be due to NSAIDs or alcohol

Question 19

What is chronic gastritis?

Answer 19

Mucosal inflammation caused by;
H. Pylori (can cause peptic ulcer or adenocarcinoma)
Antibodies inhibiting parietal cells
Chronic alcohol abuse

Question 20

How can gastritis cause perinicous anaemia?

Answer 20

Inhibiton of parietal cells reduces the amount of intrinsic factor released which is needed for Vit B12 absorption

Question 21

What is a peptic ulcer?

Answer 21

Mucosal injury that pierces through the muscularis mucosa layer, most commonly in the 1st part of the duodenum, also the lesser curvature of the stomach.

Question 22

What can cause a peptic ulcer?

Answer 22

Stomach acid
H. Pylori
NSAIDs

Question 23

What are the symptoms of a peptic ulcer?

Answer 23

Epigastric pain - esp following a meal
Bleeding
Weight loss

Question 24

How are gastric ulcers, GORD and gastritis treated?

Answer 24

Eradicate H pylori: triple therapy of PPI + clarithromycin + amoxicillin

PPIs: eg omeprazole which inhibits the proton pump

H2RA: eg ranitidine which prevents histamine stimulating parietal cell

Question 25

What is Zollinger-Ellison syndrome?

Answer 25

Non-beta islet cell, gastrin-secreting tumour of the pancreas.
Causes proliferation of parietal cells increasing acid production, severe ulceration of stomach

Question 26

How might gastric pathologies be diagnosed?

Answer 26

GI endoscopy
Blood test for anaemia
Urease breath test for H Pylori

Question 27

How does H pylori damage epithelia?

Answer 27

Produces urease which converts urea to ammonium which is toxic to epithelia and increases local pH.
Can also release cytotoxins and degrade the mucus layer

Question 28

What is the effect of H pylori depending on where it is mostly distributed?

Answer 28

Antrum: affects G cells increasing gastrin secretion. Leads to duodenal ulceration

Body: gastric ulcer, cancer

Question 29

Describe the presentation and risk factors of stomach cancer

Answer 29

Dysphagia, loss of appetite, malaena, weight loss, enlarged Virchow’s nodes

H. Pylori, infection, smoking