Abstract: Objective　To provide meaningful reference and data for thyroid surgery through the dissetion of the entrance point of laryngeal recurrent nerve (RLN) into the larynx.　Methods　Forty formaldehyde fixed adult male corpse specimens, bilateral RLN were dissected, with ipsilateral cephalic margins of the trachea and the intersection of RLN as the vertex of the angle. The angle between the entry of bilateral RLNs into the larynx and the ipsilateral lateral margin of trachea, the vertical distance between the entry of bilateral RLNs into the larynx and the anterior superior margin of the first and second tracheal ring rings, and the horizontal distance between the entry of bilateral recurrent laryngeal nerves and the lateral margin of the ipsilateral first and second tracheal ring rings were recorded.　Results　 (1) The angle (α) between the throat entrance of bilateral RLN and the side edge of ipsilateral trachea was analyzed. There were 21 cases with 0≤ α <5°, accounting for 26.25%, 46 cases with 5°≤α <10°, accounting for 57.50%, and 11 cases with 10°≤ α <15°, accounting for 13.75 %,  2 cases with α ≥15°, accounting for 2.50 %. The left side angle was  (6.0±0.5)°(0~21°), and the right side angle was  (7.0±0.5)°(0~25°). (2) The vertical distances from the anterior upper edge of the first tracheal ring to the left RLN and right RLN were (19.72±0.52) mm and (21.21±0.43) mm, respectively. The vertical distances from the anterior upper edge of the second tracheal ring to the left RLN and right RLN were (20.91±0.49) mm and (21.42±0.39) mm, respectively. The horizontal distances from the lateral edge of the ipsilateral first tracheal ring to the left RLN and right RLN were (2.96±0.11) mm and (2.96±0.10) mm, respectively. The horizontal distances from the lateral edge of the second tracheal ring to the left RLN and right RLN on the same side were (3.49±0.12) mm and (3.50±0.52) mm, respectively. Conclusions The entry angle of bilateral RLNs into the larynx and the position of the first and second tracheal rings are relatively fixed. Better understanding of the fine anatomy of the RLN laryngeal entry can help to find the RLN laryngeal entry more efficiently and safely, can reduce the injury of the RLN during thyroid surgery, and thus reduce the incidence of surgical complications.

Key words: Recurrent laryngeal nerve into the larynx,  ,  , Anatomy,  ,  , Thyroid surgery,  ,  , Angle,  ,  , Tracheal ring