b) inserting {HEAD ~ a working end} of 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 {TAIL ~ the stomach} of the patient 
b ) inserting { HEAD ~ a working end } of 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 { TAIL ~ the stomach } of the patient
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 OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH