Ulceration involves the full thickness of the gastrointestinal mucosa. It is caused by disruption of the normal balance between the corrosive effect of gastric juice and the protective effect of the mucus on the gastric epithelial cells. It may be viewed as an extension of the gastric erosions found in acute gastritis. The most common sites for ulcers are the stomach and the first few centimetres of the duodenum. More rarely they occur in the oesophagus and round the anastomosis of the stomach and small intestine,following gastrectomy. The underlying causes are not known but,if gastric mucosal protection is impaired,the epithelium can be exposed to gastric acid causing the initial cell damage that leads to ulceration. The main protective mechanisms are: a good blood supply,adequate mucus secretion and efficient epithelial cells replacement.
BLOOD SUPPLY.
Reduced blood flow and ischaemia may be caused by excessive cigarette smoking and severe stress,either physical or mental. In stressful situations the accompanying sympathetic activity causes constriction of the blood vessels supplying the alimentary tract.
SECRETION OF MUCUS.
The composition and the amount of mucus may be altered,eg:
- By regular and prolonged use of aspirin and other anti-inflammatory drugs.
- By the reflux of bile acids and sites.
- In chronic gastritis.
