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a gap or open space; anatomic nomenclature for various types of openings includes aditus, aperture, foramen, fossa, hiatus, inlet, meatus, orifice, ostium, and outlet.
1. the aperture in the diaphragm for passage of the descending aorta.
2. aortic orifice.
cardiac opening the opening from the esophagus into the stomach.
pulmonary opening (opening of pulmonary trunk) pulmonary orifice.
pyloric opening the opening between the stomach and duodenum.