From the Research
The neuromuscular activities in the stomach after eating vary by region to facilitate proper digestion, with the fundus exhibiting receptive relaxation, the body showing slow mixing waves, and the antrum demonstrating vigorous contractile activity. In the fundus, receptive relaxation occurs immediately after food intake, allowing this upper portion to expand and accommodate the meal without increasing intragastric pressure. This adaptive relaxation is mediated by vagal inhibitory neurons releasing nitric oxide and vasoactive intestinal peptide, as supported by studies such as 1 and 2.
The body of the stomach exhibits slow, gentle mixing waves that begin as electrical slow waves generated by interstitial cells of Cajal, creating shallow contractions that mix food with gastric secretions to form chyme. These contractions are relatively weak and primarily serve to knead the food rather than propel it forward. The antrum demonstrates the most vigorous contractile activity, with strong peristaltic waves that intensify as they approach the pylorus.
These powerful contractions, regulated by both neural and hormonal mechanisms including gastrin and acetylcholine, serve to grind food particles against the closed pyloric sphincter and force small amounts of liquefied chyme into the duodenum while returning larger particles for further processing. This coordinated activity ensures food is properly broken down physically and chemically before entering the small intestine for absorption, as discussed in studies like 3 and 4.
Key points to consider include:
- The role of vagal inhibitory neurons in mediating adaptive relaxation in the fundus
- The importance of nitric oxide and vasoactive intestinal peptide in this process
- The distinct contractile activities in the body and antrum of the stomach
- The regulation of these activities by neural and hormonal mechanisms
- The overall goal of ensuring proper digestion and absorption of nutrients.