Final answer:
Laryngopharyngeal reflux (LPR) occurs when reflux comes up and out of the UES into the larynx, whereas intra-sphincteric reflux is when the reflux stays within the cricopharyngeus muscle of the UES.
Step-by-step explanation:
When reflux comes up and out of the Upper Esophageal Sphincter (UES) into the larynx, it is known as laryngopharyngeal reflux (LPR). In contrast, if it stays within the confines of the cricopharyngeus muscle, which is part of the UES, it's termed intra-sphincteric reflux.
The process of swallowing involves various structures to prevent food from entering the respiratory tract. The gastro-esophageal sphincter, or cardiac sphincter, plays a crucial role by opening to allow the bolus to pass from the esophagus into the stomach and closing to prevent the acidic digestive juices from escaping back into the esophagus, thus averting acid reflux or heartburn.