Final answer:
Stomach contents are emptied into the duodenum within 2-4 hours post-meal, with carbohydrates leaving first and fatty meals taking the longest. The semi-fluid mixture, chyme, is regulated by hormonal mechanisms and is gradually moved to the small intestine for further digestion.
Step-by-step explanation:
After 2-4 hours, the contents of the stomach are typically emptied into the duodenum. During this time, carbohydrates are digested the fastest, allowing them to leave the stomach first. This is followed by the digestion of high-protein foods. Fatty meals, on the other hand, due to their high triglyceride content and the slower processing of fats by enzymes in the small intestine, may remain in the stomach for up to 6 hours or more. The stomach contents are transformed into a semi-fluid substance known as chyme, which is then passed through the pyloric sphincter into the small intestine for continued digestion and nutrient absorption.
The movement of chyme is regulated by neural and hormonal mechanisms such as the release of gastrin, which stimulates the production of hydrochloric acid (HCl), necessary for converting pepsinogen to pepsin and for protein digestion. Gastric emptying into the small intestine is a controlled process, with only a small amount of chyme being transferred each time. This entire process is a part of the overall digestion that occurs over 24 to 72 hours from start to finish.