Ever wondered how your stomach contents defy gravity and don’t leak out when you hang upside down?
Understanding the complexity of how the high pressure zone forms the antireflux barrier helps explain this phenomenon and leads to a better understanding of why heartburn happens.
In Part I, we discussed all the physical structures. In Part 2, we get into the details of how they all work together.
The antireflux barrier (ARB) is composed of well-defined structures that work synergistically to keep stomach contents out of the esophagus. The components of the ARB are:
- The gastroesophageal valve (GEV),
- The lower esophageal sphincter (LES),
- The crura of the diaphragm, which “pinch” the distal esophagus aiding in closing the esophagus,
- The intraabdominal esophagus which is exposed to positive intraabdominal pressure
- Esophageal peristalsis, motility and clearance
The anatomy of the esophagogastric junction has been known for a long time. What has changed is the understanding of how it works. In 1985, Boyle started to understand the role of the diaphragm compression on the structures in the region in a study made in cats.[1-2] Since then, more and more studies have helped clarify the functions of the EGJ.
The HPZ at the LES is created by a series of structures and physiological events:
- The LES, although small, provides a sphincter-like function by a higher and maintained contraction tonus
- The crura of the diaphragm add to this pressure, the HPZ is higher on the left side because of the anatomy of the region, causing the left crus of the respiratory diaphragm to exert a higher pressure on the left side of the esophagus
- The intraabdominal pressure is higher on the abdominal region than in the thoracic region, helping close the abdominal esophagus
It is important to understand that the failure of any of these structures to perform its function can be the cause of GERD, as the higher intraabdominal pressure will force the gastric content towards the thoracic esophagus.
GERD is a progressive disease with symptoms that start with occasional episodes of heartburn. As the anatomical structures and HPZ break down, the frequency and intensity of reflux symptoms increase.
A special thanks to Dr. Miranda for finding the Boyle references and providing these links to more terms that are relevant to this anatomy:
Dr. Efrain A. Miranda is the CEO of Clinical Anatomy Associates, Inc. A former professor of Neuroanatomy at the University of Chile Medical College, he also serves as an Adjunct Professor of Anatomy at the Cell Biology, Anatomy and Neuroanatomy Department of the University of Cincinnati College of Medicine. Dr. Miranda is an active member of the American Association of Clinical Anatomists and host of www.medicalterminologydaily.com
Debbie Donovan is in the marketing department and is editor of this blog. She’s also managing the GERDHelp social media channels where we post hot stories on heartburn, acid reflux, GERD, Barrett’s esophagus and esophageal cancer. Deb ice skates and likes routines with fancy footwork and spins.
Sharon Palermo is in the marketing and training department and part of each day is spent sharing the myriad of things said about heartburn, acid reflux, GERD, Barrett’s esophagus and esophageal cancer on the GERDHelp social media channels. Sharon clowns around as a talented balloon artist, cake decorator and face painter. We hope you enjoy her artistry on this blog.