Which cells secrete gastric enzymes, including pepsin and other gastric enzymes, and which area of the stomach are they found?
Chief cells, they are found in the crypts in the body and antrum of the stomach
Which cell type produces somatostatin and where are they found?
D cells in the crypts in the antrum
What are the indications for PPI use?
- Gastric Ulcers
- Duodenal ulcers
- Prevention & treatment of NSAID-induced ulcers
What are the 4 layers of the stomach?
Mucosa; body/fundus and antral/pyloric, muscualris mucosa
Submucosa and nerve plexus
Muscularis propria; oblique, circular and longitudinal and nerve plexus
What can the aluminium in antacids cause?
What epithelium type is present in the oesophagus?
Non-keratinising stratified squamous epithelium
Which part of the stomach is spared in autoimmune gastritis?
What are the 4 stages of gastric secretion?
What is the primary mechanism of gastric juice secretion in the cephalic phase?
Vagal input that originates from the brain region known as the dorsal vagal complex.
What are the 3 main causative agents of chronic gastritis?
H. pylori infection, in 90% of GU and 70% of DU
NSAIDs causing chemical gastritis
What is an erosion?
A superficial break in the mucosa alone.
Omeprazole, Lansorazole, Pantoprazole and Esomeprazole are all what?
Proton Pump Inhibitors
What is the most common tumour of the stomach?
What is the function of the submucosal glands in the oesophagus?
To produce and secrete acid mucins
What receptor does gastrin bind to on parietal cells?
The CCKb receptor
Which enzymes do NSAIDs inhibit, and why is it important in GIT integrity?
The inhibit COX-1 and COX-2.This lowers the level of protective prostaglandins
What is a peptic ulcer?
A break in the superficial epithelial cell lining penetrating down to the muscularis mucosa, with a fibrous base and increases in inflammatory cells
What are the anti-reflux mechanisms in the oesophagus?
- Tonic contraction of the LOS
- The oesophagus acting as a flap valve
- Folds of gastric mucosa acting as a mucosal rosette
- Contraction of the diaphragm at the LOS
What is found within the lamina propria of the stomach?
- Capillary vessels and nerves
- Plasma cells
- Macrophages (Histiocytes)
What are the risk factors for squamous cell carcinoma of the oesophagus?
- Achalsia of the cardia
- Plummer-Vinson syndrome; oesophageal web, post-cricoid dysphagia and Fe deficient anaemia in elderly female
What does excess magnesium in the GIT cause?
What are rugae?
Mucosal folds caused by contraction of the muscular layer of the stomach.
What cells produce gastrin and where in the stomach are they found?
G cells in the crypts in the antrum of the stomach
What are the symptoms of GORD?
- Heartburn; most commonly post-prandially
- Acid regurgitation
Dysphagia - Alarm symptom
- Chest pain
- Water brash
How can Domperidone and Metoclopramide be useful in treating reflux caused by slow transmission in the GIT
They are gastric stimulants and increase peristalsis in the jejunum and duodenum.It is thought they work through muscarinic activation
Which cells secrete hydrocholoric acid and where are they mainly found in the stomach?
Parietal cells, the crypts in the body and antrum of the stomach
What are the 2 types of H.pylori gastritis; how do they differ?
Pan gastritis - body and antrum; decreased acid output
Antral gastritis - antrum; increased acid output.
What are the complications of chronic ulcers?
- Bleeding leading to anaemia and shock
- Perforation leading to peritonitis
- Scarring and obstruction leading to vomiting
- Weight loss
- Loss of acid
What class of drug are Ranitidine, Nizatidine, Famotidine and Cimetidine?
They are H2 receptor antagonists
What cell types does gastrin bind to exert its activity?
- Enterochromaffin-like cells (ECLs)
- H cells; increase histamine release
What are the differences in the histology of the body/fundus and the antral/pyloric?
Body and fundus; short pits, parietal cells and chief cells, endocrine cells
Pylorus and antrum; long pits, mucous cells and endocrine cells.
What is the gastrin's function?
To stimulate the production of acid from the parietal cells.
Which group of drugs neutralise the stomach acid?
What are the 3 chemical mediators of acid secretion?
Acetyl choline binding to M3 receptors
Histamine binding to H2 receptors
Gastrin binding to CCKb receptors
How is Barrett's oesophagus diagnosed?
Through an endoscope showing displacement of the Z-line.
What is dyspepsia?
It is a symptom not a disease;
"Pain or discomfort centred in the abdomen"
What do Sucralfate and misoprostol do?
They promote mucosal defence through an increase in prostaglandin production and bicarbonate secretion (Sucralfate only)
What cell type produces and secretes intrinsic factor, the glycopeptide that allows Vit B12 to be absorbed?
Which group of drugs reduce the irritancy of stomach acid?
Who are most likely to get squamous cell carcinoma of the oesophagus?
Men aged over 50
How is histamine release regulated in the stomach?
- Neurally by the vagal nerve and acetyl choline
How does the muscular layer of the oesophagus change throughout its course?
- It changes from striated muscle in upper third to a mix of striated and smooth muscle in the middle third
- The lower third is smooth muscle
What is Barrett's oesophagus?
The normal oesophageal squamous epithelium is replaced by metaplastic columnar epithelium to form a segment of "columnar-lined oesophagus" CLO.
What receptor in the oesophagus is activated in oesophagitis, giving the sensation of pain?
The vanilloid receptor-1
How do NSAIDs cause peptic ulcers?
They inhibit COX-1 in the mucosa and therefore suppress the production of prostaglandins.
Where are gastric ulcers most commonly seen?
The lesser curvature of the stomach near the incisura
Where are duodenal ulcers most commonly found?
The duodenal cap
How can autoimmune gastritis lead to multiple carcinomas in the stomach?
- Anti-parietal cell antibodies attack the parietal cells.
- This leads to acholrhyia and over secretion of gastrin.
- Gastrin then over-stimulates endocrine cells which may lead to the mulitple carcinomas.
When are H2 receptor antagonists used?
- Gastric ulcers
- Duodenal ulcers
- GORD symptoms
- Zollinger-Ellison syndrome (High dose)
What are the oesophageal mucosal defence mechanisms against acid erosion?
- Unstirred water layer
- Apical cell membranes restrict H+ diffusion into cells
What are the symptoms of Peptic ulcer disease?
- Weight loss and anorexiaI
What are the radiating folds of a gastric/duodenal ulcer?
They are where the gastric/duodenal wall has been pulled into folds due to scar contraction
What test can be performed to test for H. pylori infection?
- Urea breath test
- CLO antibody test
What is the "Z" line?
The junction between the squamous (white) and columnar (pink) mucosa at the gastro-oesophageal junction
What are the 2 mechanisms of gastrin secretion from G cells?
- Neurotransmitter release from enteric nerve endings, called Gastrin Releasing Peptide
Presence of oligopeptides in the gastric lumen.
What are the main causes of an acute gastric ulcer?