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