Objective      To investigate the feasibility and safety of totally thyroidectomy through transtracheal endoscopy by studying the anatomical approach and adjacent structures.       Methods      A total of 5 embalmed adult cadavers were dissected layer by layer in the cervical region

pharyngeal region and mandible region according to transtracheal assisted sublingual approach that was verified from the anatomical approach and planes. Another 15 fresh adult cadavers were dissected by blood vascular casting technique

imaging scanning technique and thin layer cryotomy. The anatomical structures of the thyroid gland surgical region were analyzed and studied qualitatively and quantitatively.       Results       The transtracheal operational access was placed from the cavitas oris propria

isthmus faucium

subepiglottic region

laryngeal pharynx

and intermediate laryngeal cavity

and then passed from the top down in order to reach pars cervicalis tracheae where a sagittal incision was observed in the anterior wall of cartilagines tracheales to reach ascertained surgical region. CT scanning showed abduction vocal cords were in trapezoidal shape with a sagittal height (length) of 20.12±3.25 mm for male and 15.68±2.56 for female

a frontal  width of 2.10±0.50 mm

a  back width of 9.00±0.80 mm

and a middle  thickness of 5.00±0.85 mm. The transverse diameter of abduction true glottis was 5.50±1.45 mm

which was the narrowest part in cavum laryngis.       Conclusion       As natural orifice transluminal endoscopic surgery

totally endoscopic thyroidectomy through transtracheal approach is feasible and safe anatomically.