Final answer:
Uncontrolled bolus flow into the pharynx may be due to a short reflex relaxation of the lower esophageal sphincter, resulting in potential issues like choking or aspiration. This can be caused by conditions such as prolonged vomiting and diarrhea or chronic renal disease.
Step-by-step explanation:
Uncontrolled bolus flow into the pharynx may be due to a short reflex relaxation of the lower esophageal sphincter, which allows the bolus to pass into the stomach. This reflex relaxation can occur during the esophageal phase of swallowing when the esophageal glands secrete mucus that lubricates the bolus and minimizes friction.
This relaxation of the lower esophageal sphincter can result in the bolus entering the pharynx without proper control, leading to potential issues like choking or aspiration.
Conditions that can lead to uncontrolled bolus flow include prolonged vomiting and diarrhea, which result in excessive loss of digestive fluid, and chronic renal disease with acidosis due to poor tubular reabsorption of sodium.