*The Differences between Gastroesophageal and Laryngopharyngeal Reflux DOI: http://dx.doi.org/10.5772/intechopen.106418*

the sphincter and the latter occupying the lower one-third. Contraction of the hyoid muscle that pulls the larynx forward, linked to the relaxation of the cricopharyngeus and the thyropharyngeus, leads to sphincter opening wide.

The primary role of the UES is to protect the upper airway spaces from retrograde movement of stomach contents. It also prevents a bigger amount of air from reaching the gastrointestinal tract. Lower esophageal sphincter, which measures 2.5–3.5 cm in length, is composed of smooth muscle and is not a true anatomical sphincter, but it is a physiological sphincter that is under involuntary control by the sympathetic trunk and the vagal nerve. In response to direct inhibitory signals, the smooth muscles in the LES relax, allowing the sphincter to open, and the bolus to pass. The LES and the crural diaphragm constitute a high-pressure zone that act as a mechanical anti-reflux barrier that minimizes movement of stomach contents back into the esophagus and also allows the bolus into the stomach [5].

Esophageal peristalsis is a process of simultaneous constriction and distal relaxation, which drives the bolus toward the stomach. This process ends by relaxation and opening of the LES and enabling the passage of the bolus into the stomach. The esophagus is lined with stratified squamous epithelium. The submucosal glands secrete water, bicarbonate, mucins, epidermal growth factor, and prostaglandins. This secretion is involved in mucosal clearance. At the gastroesophageal junction is a change to simple columnar epithelial cells with gastric glands and pits. This squamocolumnar junction is of special importance in patients with reflux disease—it is a critical point for the development of Barrett's esophagus, a premalignant condition that is associated with esophageal carcinoma [6].
