b) inserting a working end of a flexible tube of an endoscope into the mouth of the patient and translating the working end of {HEAD ~ the flexible tube} to {TAIL ~ the esophagus} or the stomach of the patient 
to
b ) inserting a working end of a flexible tube of an endoscope into the mouth of the patient and translating the working end of { HEAD ~ the flexible tube } to { TAIL ~ the esophagus } or the stomach of the patient
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH