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Gastroesophagogastric Analysis

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First, dissection of the phrenoesophageal membrane and dislocation of the GEJ into the chest do not alter manometric LES pressures. Second, selective myotomy of the clasp fibers or selective excision of the gastric sling reduces LES pressure and compromises GEJ competence but does not totally abolish these, whereas myotomy or resection of both structures abolishes the manometric LES and GEJ competence.

Fig. 2.4, Schematic illustration of the muscular arrangement at the esophagogastric junction. The oblique gastric sling muscle helps to form the angle of His. The semicircular clasp fibers, by their anchorage to the medial margin of the gastric sling fibers, can contract in a ring-shaped fashion. From Libermann et al. (2008).
Finally, 3-dimensional
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2.5, Schematic drawing shows correlation between radial muscle thickness (left) and 3D manometric pressure image (right) at human gastroesophageal junction. Muscle thickness across the gastroesophageal junction at the posterior gastric wall (PW), greater curvature (GC), anterior gastric wall (AW), and lesser curvature (LC) is shown in millimeters. Radial pressures at gastroesophageal junction (in millimeters of mercury) are plotted around an axis representing atmospheric pressure. Asymmetry of the sphincter is apparent. From Stein et al., 1995.

Phrenoesophageal membrane
This tough ligament limits displacement of the esophagus into the thorax and draws it back into position while minimizing circumferential traction on the LES. Laxity of the ligament with age facilitates the development of hiatus hernia. Aside from its function to provide a loose collar around the LES allowing plasticity to move in relation to the diaphragm, it does not contribute to the sphincter pressure profile. (Richter, 2013)
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This crus arises from the anterior longitudinal ligament overlying the lumbar vertebrae and encircles the distal esophagus in a scissorlike fashion to form a 2-cm long hiatal canal. The proximal one-third of the LES is located proximal to the diaphragm and the distal two-thirds of the sphincter is below the diaphragm and intra-abdominal. The extrinsic sphincter component of measured LES pressure is formed by the striated muscular fibers of the diaphragm. The basal tonic pressure of the LES is mainly from the esophageal components of the sphincter, and the superimposed increments in pressure during inspiration are caused by contractions of the crural diaphragm. The magnitude of the increase in pressure during inspiration is directly proportional to the force of contraction of the crural diaphragm. During tidal inspiration, the increase in GEJ pressure is much smaller than during deep inspiration. The crural diaphragm also rapidly contracts during events that increase intra-abdominal pressures (coughing, abdominal compression, and straight leg raising), thereby protecting against reflux that might occur with these increases in gastric pressure. Both the LES and crural diaphragm relax with the initiation of swallowing and the distal esophagus and LES are pulled 1 cm-2 cm upward by the contractions of the longitudinal muscles. The peristaltic wave pushes the bolus in a distal direction
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