From the physiology of gastric emptying to the understanding of gastroparesis

The stomach is the segment of the gastrointestinal tract in which the main secretory functions and digestion in the alimentary canal begins. However, it’s most critical and important function in digestive physiology is gastric motility (GM). Normal GM is controlled by diverse extrinsic and intrinsic stimuli. The main extrinsic regulation comes from the vagal nerve. Although the majority of vagal efferents that arrive at the stomach are excitatory, some vagal nerve endings are inhibitory. They produce stimuli through neurotransmitters such as nitric oxide and vasoactive intestinal peptide (VIP). Intrinsic stimuli come from the enteric nervous system and are important in the coordination of gastric motility with more distal segments of the digestive tract especially during the interdigestive period (Figure 1). These myenteric neurons also communicate with the different pacemaker cells of the digestive tract. They are also known as interstitial cells of Cajal (ICCs) and are located in the circular muscle layer of the stomach and the proximal intestine. GM has three basic components. Even though each one of these phenomena has independent moments and mechanisms, normal gastric emptying is only achieved when there is a functional integration of the three activities (1-4).