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