The Anatomy and Physiology of the Stomach - Practice Questions & MCQ

• It is also known as Gaster
• The stomach is a thick-walled organ that lies between the oesophagus and the first part of the small intestine (the duodenum). 
• It is on the left side of the abdominal cavity.
• It is the widest organ of the alimentary canal.
• It is a hollow J-shaped organ.
• The esophageal or Cardiac sphincter is the opening between esophagus and the stomach
• Opening of Stomach into small intestine is guarded by Pyloric sphincter

Parts of Stomach:

• The fundus, which is formed by the upper curvature of the organ.
• The cardiac region, where the contents of the oesophagus empty into the stomach.
• The body, the main central region.
• The pylorus or atrium, the lower section of the organ that facilitates the emptying of the contents into the small intestine.

• The mucosa consists of an epithelium, the lamina propria underneath, and a thin bit of smooth muscle called the muscularis mucosae.
• The submucosa lies under this and consists of fibrous connective tissue.
• The epithelium of the stomach forms deep pits called fundic or oxyntic or gastric glands.
• The cells of the gastric glands are as follows:
  • The cells at the base of these pits are chief cells or zymogenic cell or peptic cell that are responsible for the production of pepsinogen, an inactive precursor of pepsin, which degrades proteins.
  • Further up the pits, parietal cells or oxyntic cells produce gastric acid and a vital substance, intrinsic factor. The gastric acid kills most of the bacteria in food, stimulates hunger, and activates pepsinogen into pepsin. It denatures the complex protein molecule as a precursor to protein digestion through enzyme action in the stomach and small intestines.The intrinsic factor helps in absorption of Vit B12
  • Near the top of the pits, closest to the contents of the stomach, there are mucus-producing cells called goblet cells that help protect the stomach from self-digestion.
  • The G-cells or enteroendocrine cells secrete gastrin hormone.
  • The argentaffin cells secrete serotonin, somatostatin and histamine.
• The muscularis externa is made up of three layers of smooth muscle as follows:
  • The innermost layer is obliquely-oriented: this is not seen in other parts of the digestive system. This layer is responsible for creating the motion that churns and physically breaks down the food.
  • The next layer is made up of circular muscles.
  • It is followed by longitudinal muscles

• It acts as a temporary storage organ. Because of this, the frequency of eating is reduced.
• Digestive function is because of pepsin enzyme. It is a proteolytic enzyme.
• The movements of the stomach convert solid food into a fluid paste called chyme and deliver this in small quantities to the duodenum for proper digestion in the small intestine.
• A protective function is because of the high acidic medium due to the presence of HCl, many of the micro­organisms die. Thereby it protects the GI tract from getting invaded by the microorganisms.
• The hematopoietic function is because of the intrinsic factor which is secreted by gastric glands. Intrinsic factor is essential for the absorption of vitamin B12 in the ileum region.
• The absorptive function is also one of the functions of the stomach. Some amount of water and alcohol is absorbed in the stomach region.