The stomach is a muscular organ located in the left upper abdomen, positioned between the oesophagus and the duodenum. As food reaches the end of the oesophagus, it enters the stomach through a muscular valve called the lower oesophageal sphincter. The stomach continues to break food down mechanically and chemically, through churning the food and secreting acid and enzymes for digestion. This allows for absorption of nutrients to occur as the food continues through the gastrointestinal tract.
The acidic environment in the stomach helps with digestion and destroys any potential pathogenic microorganisms that may have been ingested. Acid secretion is an intricate process that needs to be highly regulated. If this goes wrong, it can lead to hypersecretion of acid or achlorhydria.
Gastric mucus is also produced within the stomach. It is secreted by the epithelial cells and glandular cells in the stomach. This mucus acts as a barrier that protects the stomach wall from the acid and digestive enzymes found within the stomach lumen. If the mucus layer is breached for some reason, it can result in peptic ulcer formation which can cause various problems.
In this section, learn more about the physiology of the stomach- the production of acid, and mucus production.