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Regulation of Gastric Emptying

The stomach typically empties within four hours post-meal. Gastric emptying speed increases with larger meals and liquid contents, as fluids move quickly whereas solids remain until well mixed with gastric juice. The duodenum's state significantly affects gastric emptying; as chyme enters, receptors trigger enterogastric reflex and hormonal responses (e.g., enterogastrones) that inhibit gastric secretion, thereby controlling stomach contractions and preventing small intestine overload.

Enterogastrones and Their Effects

Enterogastrones, such as secretin and cholecystokinin, reduce stomach contractile force and therefore slow gastric emptying. Chemical and stretch receptors in the duodenum respond to chyme composition, initiating reflex pathways that involve both short and long neural circuits, affecting sympathetic and parasympathetic activity.

Factors Affecting Gastric Emptying

High-fat chyme slows gastric emptying significantly, leading to prolonged retention in the stomach. In contrast, carbohydrate-rich meals pass rapidly.

Vomiting (Emesis)

Vomiting can be triggered by factors like stomach stretching or irritants (e.g., toxins, drugs). It involves sensory signals to the emetic center in the medulla, leading to a series of muscular responses. Symptoms include nausea, pallor, and excessive salivation, with increased intra-abdominal pressure facilitating the expulsion of stomach contents.

Clinical Considerations

Severe vomiting can lead to dehydration and electrolyte imbalance. Loss of hydrochloric acid can cause blood alkalosis as the stomach tries to compensate for the lost acid.