Final answer:
The epiglottis is responsible for closing off the tracheal opening during swallowing, ensuring that food is directed into the esophagus and not the trachea. The esophagus has upper and lower sphincters that control the passage of food and prevent acid reflux.
Step-by-step explanation:
When food is swallowed, the epiglottis plays a crucial role in directing the food into the esophagus and away from the trachea.
The process begins with the rise of the soft palate and uvula to close off the nasopharynx. At the same time, the larynx is pulled upwards, and the epiglottis folds down to cover the glottis, which is the opening to the larynx.
This action ensures that food does not enter the trachea but is instead diverted into the esophagus. If food does accidentally enter the trachea, a cough reflex is triggered to eject the food.
The esophagus is a muscular tube that serves as a conduit for food from the pharynx to the stomach. It contains sphincters at both ends to regulate the passage of food.
The upper esophageal sphincter opens in response to swallowing, allowing the food bolus to enter from the pharynx, while the lower esophageal sphincter, or gastro-esophageal sphincter, opens to let the food into the stomach and closes to prevent stomach acid from entering the esophagus.