The posterior aspect of the larynx, including the arytenoid and cricoid cartilages also forms the anterior wall of the UES. A major purpose of the coordinated swallow is to prevent penetration and aspiration into the larynx and trachea and allow appropriate passage through the UES into the esophagus ( 1). The larynx is the most highly protected region of the upper aerodigestive tract. The muscular control of the UES is primarily extrinsic by the suprahyoid and infrahyoid muscles, while intrinsic control of opening and closing is by the CPM, inferior constrictor muscle and the cranial circular esophageal muscle. The bulk of the pressure providing the sphincteric function of the region is from the elastic recoil of the larynx abutting the cervical spine. The UES is a kidney bean shaped potential space, about 4 cm in length, that is bounded anteriorly by the larynx, posterolaterally by the pharyngoesophageal muscles, superiorly by the pharynx and inferiorly by the esophagus ( 5- 7). The UEHPZ is a manometric term referring to the areas of high pressure noted in the anatomic region of the UES.
Although the CPM is an important component of the UES, it only represents the distal third of the UES. The CPM, however, is not synonymous with the UES and PES.
The PES is synonymous with this definition of the UES. Instead of being a true sphincter, the UES is a 4-cm segment of the digestive tract consisting of cartilaginous, bony and muscular components that opens and closes based on both intrinsic muscular control and displacement. No aspect of the UES entirely meets this definition. The word sphincter is defined as an annular muscle surrounding and able to contract or close a bodily opening ( 4). A review of terminology is a necessary foundation for a comprehensive understanding of UES anatomy and physiology ( 3). These are the CPM, the pharyngoesophageal segment (PES), and the upper esophageal high-pressure zone (UEHPZ). There are several terms that are often used in discussion of the UES. Prior material based on the senior author’s (PB) experience and scholarship in addition to relevant recent publications on the relevant topics of anatomy and physiology. Given the scope of the material, a narrative review format was chosen. A thorough understanding of the UES anatomy and physiology is critical for all deglutologists seeking to improve pharyngo-esophageal swallow function. During the act of swallow, the relaxation of the cricopharyngeus muscle (CPM), elevation of the larynx and propulsion of the food bolus by the pharynx coordinate to open the UES and facilitate deglutition ( 2). The larynx and vocal folds represent the entry into the airway, while the upper esophageal sphincter (UES) guards the entrance of the esophagus, both from aerophagia in the anterograde direction and regurgitation in the retrograde ( 1). In humans, the reality of a combined upper aerodigestive tract necessitates the finely tuned regulation of the division into the digestive and respiratory systems. Received: 09 April 2021 Accepted: 05 August 2021 Published: 25 September 2022. Keywords: Anatomy upper esophageal sphincter (UES) pharyngoesophageal segment (PES) physiology An understanding of the anatomy of the region in addition to the phases of UES opening facilitates more refined therapeutic interventions for patients with pharyngoesophageal swallow impairment and dysphagia. During the act of swallow, the relaxation of the CPM, elevation of the larynx and propulsion of the food bolus by the pharynx coordinate to open the UES and facilitate deglutition. In fact, relaxation of the CPM is not the primary contributor to UES opening. Although the cricopharyngeus muscle (CPM) is often considered synonymous with the UES, in reality it is but one component of the complicated anatomy. Guarding the entrance of the esophagus, the UES controls inflow and outflow through the region, preventing aerophagia in the anterograde direction as well as regurgitation in the retrograde. The structure is bounded anteriorly by the larynx, posterolaterally by the pharyngoesophageal muscles, superiorly by the pharynx and inferiorly by the esophagus. This narrative review represents an overview of the anatomy and physiology of this critical component of the airway protective mechanism. Policy of Dealing with Allegations of Research MisconductĪbstract: The upper esophageal sphincter (UES), also known as the pharyngoesophageal segment (PES), is a 4-cm segment of the digestive tract that separates the esophagus from the pharynx and larynx.Policy of Screening for Plagiarism Process.
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