Final answer:
A nasogastric tube is inserted through the nostril, down the throat, through the esophagus, and into the stomach, reaching the upper part of the small intestine.
Step-by-step explanation:
When using a nasogastric tube, the tube is inserted through the patient's nostril, then passed down the throat into the stomach, and pushed further into the upper part of the small intestine. This procedure is done not only to administer nutrition or medication but also for diagnostic purposes. For example, secretin can be administered through the tube, after which the duodenal secretions are aspirated and analyzed to help diagnose conditions such as ulcers or other digestive tract diseases.
The esophagus plays a critical role during this process. The esophagus is a muscular tube that connects the pharynx to the stomach. When the tube is being inserted, it must pass through the esophagus on its way to the stomach. The esophagus is located behind the trachea and penetrates the diaphragm through an opening called the esophageal hiatus to enter the abdomen.