AB2.H1.4 Stomach
Stomach:
- The stomach is the site where primary digestion of the food takes place
- This part of the gut tube is expanded to form a bag, but otherwise the structure of the stomach wall fits the basic plan for the gut tube
- The mucous membrane lining the stomach is thrown into a series of pits from which glands penetrate into the underlying connective tissue
- The epithelium of the pits is composed of simple columnar epithelial cells which are mucus secreting
- This mucus provides a protective layer for the epithelium to limit its erosion by acid and enzymes
- Glands arise from the pits
- The epithelium of these glands is continuous with the epithelium lining the pits
- Adjacent to the oesophageal opening, and the pyloric opening (leading into the duodenum of the small intestine), the glands are also composed of mucus secreting cells
- However, in the body, or main part of the stomach, the glands are formed of cells which produce and secrete hydrochloric acid (parietal cells, also known as oxyntic cells) interspersed with cells producing a range of enzymes (chief cells)
- The muscularis mucosae, and the muscularis externa both consist of three layers of smooth muscle rather than the two layers which are more usually present in other regions of the gut
- This additional (innermost oblique) layer of muscle, provides an additional plane of contraction which aids the mixing of gastric juices with the food
- Thus, the muscle in the stomach is organised more to mix the gastric juices and the food rather than to drive the contents of the gut lumen along, as is the case in most other regions of the gut
Questions:
Answer Submitted
Micrograph of Stomach:
- In this micrograph you can see the main components of the body of the stomach where the cells secreting acid and protein enzymes are located
- The lumen of the stomach is to the right of the micrograph
- Identify the gastric pits - these are lined by mucus secreting cells which are stained magenta in this preparation
- Gastric glands arise from the base of the gastric pits and extend toward the submucosa (not shown in this image)
- In the epithelial lining of the gastric glands identify acid secreting cells (rounded, pale pink staining) parietal cells, and chief cells which produce and secrete protein enzymes (purple staining cytoplasm)
- The gastric glands in the pyloric region of the stomach (adjacent to the duodenum of the small intestine) and the region of the stomach adjacent to the oesophagus contain only mucus secreting cells
