Which of these is not true about Cardio esophageal sphincter?
Correct Answer: An anatomic sphincter can be found
Description: ANSWER: (A) An anatomic sphincter can be foundREF: Gray's anatomy 40th ed ch: 71GASTROESOPHAGEAL JUNCTION : The upper esophageal sphincter (UES ) and lower esophageal sphincter (LES) mark the entrance and exit to the esophagus, respectively.These sphincters are defined by a high-pressure zone but can be difficult to identify anatomically. The UES corresponds reliably to the cricopharvngeus muscle, but the LES is more complex to discern. The opening from the oesophagus into the stomach is the cardiac orifice It is typically situated to the left of the midline behind the seventh costal cartilage at the level of the eleventh thoracic vertebra. It is 10 cm from the anterior abdominal wall and 40 cm from the incisor teeth. The short abdominal part of the oesophagus curves sharply to the left as it descends and is continuous with the cardiac orifice. The right side of the oesophagus is continuous with the lesser curvature, the left side with the greater curvature. There is no specific anatomical cardiac sphincter related to the orificeThere are four anatomic points that identify the gastroesophageal junction (GEJ): two endoscopic and two external. Endoscopically, there are two anatomic considerations that may be used to identify the GEJ. The squamocolumnar epithelial junction (Z-Iine) may mark the GEJ provided the patient does not have a distal esophagus replaced by columnar-lined epithelium as seen with Barretts esophagus. The transition from the smooth esophageal lining to the rugal folds of the stomach may also accurately identify the GEJ. Externally, the collar of Helvetius (or loop of Willis), where the circular muscular fibers of the esophagus join the oblique fibers of the stomach, and the gastroesophageal fat pad are consistent identifiers of the GEJUnlike the rest of the esophagus, the musculature of the gastroesophageal junction (lower esophageal sphincter; LES) is tonicaily active but relaxes on swallowing. The tonic activity of the LES between meals prevents reflux of gastric contents into the esophagus. The LES is made up of three components. The esophageal smooth muscle is more prominent at the junction with the stomach (intrinsic sphincter). Fibers of the crural portion of the diaphragm, a skeletal muscle, surround the esophagus at this point (extrinsic sphincter) and exert a pinchcock-like action on the esophagus. In addition, the oblique or sling fibers of the stomach wall create a flap valve that helps close off the esophagogastric junction and prevent regurgitation when intragastric pressure rises.Several anatomical and physiological factors normally prevent gastro-oesophageal reflux.The folds of gastric mucosa present in the gastro-oesophageal junctionThe mucosal rosette, contribute to the formation of a fiuid-and gas-tight seal. They also help to ensure that even low levels of tone within the lower oesophageal wall muscles may occlude the lumen of the junction against low pressures of gastric gas.The angle of the cardiac orifice may help to form a type of 'flap valve' and the length of abdominal oesophagus is buttressed externally by pads of adipose connective tissue at and below the level of the diaphragmatic hiatus.However, the major anti-reflux mechanism is the tonic contractions of the lower oesophageal musculature, which forms an effective high pressure zone (HPZ).The specialized smooth muscle of the wall of the lower oesophagus and the encircling fibres of the crural diaphragm exert a radial pressure that can be measured by a sensing device as it is withdrawn from the stomach into the oesophagus. If reflux is to be prevented, this pressure must always exceed the difference between the pressures on either side of the junction, i.e. the difference between intra-abdominal pressure (transferred to the stomach, and augmented by any contraction of the stomach wTall itself), and intrathoracic pressure (transferred to the oesophagus).
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Anatomy
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