Final answer:
The gastroesophageal sphincter allows the food bolus to enter the stomach from the esophagus, where mechanical and chemical digestion processes continue.
Step-by-step explanation:
The organ where the bolus arrives through the gastroesophageal sphincter and where mechanical and chemical digestion continue is the stomach.
Once the bolus of food is swallowed, it passes down the esophagus to reach the stomach. The esophagus facilitates this movement through a wave-like motion called peristalsis. The lower esophageal sphincter opens in response to the approaching bolus, allowing it to enter the stomach. This sphincter, also known as the gastroesophageal sphincter, functions as a valve, preventing the stomach contents from reentering the esophagus.
In the stomach, mechanical digestion is achieved through muscular contractions that churn the bolus, while chemical digestion is facilitated by gastric juices, including hydrochloric acid and the enzyme pepsin, which digest proteins. This environment further breaks down food and initiates the digestion of carbohydrates and fats, before the resulting chyme moves onto the small intestine for continued digestion and nutrient absorption.