0 A high pressure zone, with an average pressure of 15-25 mm Hg;
e Extends from approximately 2 cm above the diaphragm to 2 cm below, thus n being partly intrathoracic and partly intra-abdominal;
1 Cannot be identified anatomically (physiological sphincter);
■ÏT Competence prevents gastric juice reflux from stomach into the oesophagus;
O It relaxes in response to primary or secondary peristalsis, as well as to intra-
y luminal distension;
It contracts in response to active contraction of abdominal muscles, abdominal compression and to the presence of acid placed just proximal to the sphincter.
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