Patterns of gastric emptying are dependent on the physical and chemical composition of a meal, so that solids, nutrient liquids and non-nutrient liquids empty from the stomach at different rates. The overall emptying rate of digestible solids is characterized by a lag phase before emptying commences, followed by an emptying phase that approximates a linear pattern (Figure 1). Intragastric volume and gravity influence gastric emptying of non-nutrient liquids, which empty from the stomach in an overall monoexponential pattern. Find best deals online – *cheap viagra online can be available every time you visit.
Figure 1) Gastric emptying curves for a mixed solid (100 g minced beef) and liquid (150 mL 10% dextrose) meal consumed in the sitting position measured radioisotopically in a normal subject (A), a diabetic patient with gastroparesis (B) and a patient after truncal vagotomy with pyloroplasty (C). The normal range (mean ± 2SD) is shown in the shaded areas. There is a marked delay of solid and liquid emptying in the diabetic patient. After truncal vagotomy and pyloroplasty, the initial emptying rate of a liquid is very rapid, while there is an overall delay in solid emptying.
The major factor regulating gastric emptying of nutrients is feedback inhibition triggered by receptors that are distributed throughout the small intestine; as a result of this inhibition, nutrient-containing liquids usually empty from the stomach at an overall rate of about 2 kcal/min. There are ‘specific’ small intestinal receptors for various nutrients (glucose, fatty acids and amino acids), with regional variations in receptor number and type. The extent of small intestinal feedback is dependent on both the number and site of small intestinal receptors that are exposed, and is influenced by prior nutrient exposure. Infusion of nutrients directly into the small intestine slows gastric emptying; this is associated with suppression of antral pressure waves, stimulation of pressure waves localized to the pylorus and a reduction in the tone of the proximal stomach. Caeco-ileal reflux of short-chain fatty acids may also contribute to the regulation of gastric emptying. The stomach is capable of considerable compensation before the overall rate of emptying, as opposed to the characteristics of individual flow pulses, is modified substantially (16). In general, provided that small intestinal feedback is intact, the elimination of individual motor components does not prevent the slowing of emptying by nutrients.