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