Anatomic And Histologic Observation Of The Anterior Commissure Of The Adult Larynx

Objective:To explore the anatomic location and histologic structures of the anterior commissure of the adult larynx,the anatomic separation between the supraglottic and glottic regions at the anterior part of the larynx and the clinical significances.Methods:The laryngeal specimen was obtained from a 43-year-old male with hypopharyngeal carcinoma undergoing total laryngectomy and partial laryngopharyngectomy.Serial sections(5μm thick) of the anterior commissure specimen were stained with hematoxylin and eosin and Weigert elastic methods.All sections were observed by the light microscope and scanned by the digital scanning machine.NDP View soft ware was used to process the digital images and to measure the geometric data of the tissue components.Results:A digital image dataset of the microstructure was set up successfully.①.The anterior commissure of the larynx is located between the anterior parts of the vocal cords,including collagen fibers,elastic fibers(anterior macula flava),the insertion fibers of the vocal muscles,epithelial lamina and glandular and vascular structures in the superficial layer of the lamina propria.The width was 2.82mm from the midline of the larynx to the lateral margin of the anterior commissure.②.At the supraglottic region close to the glottic,a few dense collagen fibers and plentiful glandular and vascular structures were found beneath epithelial lamina.At the plane of the upper surface of the vocal cords,subepithelial tissues had many dense collagen fibers,a few elastic fibers,some of the insertion fibers of the vocal muscles and few vascular structures.③.The density of the subepithelial tissues was different at the each plane of the vocal cords.Both the dense collagen fiber mass and elastic fiber mass began from the upper surface of the vocal cords,inferiorly the former extended for 0.89mm and the latter 1.48mm.Their subepithelial spaces(superficial layer of the lamina propria) were narrow and a paucity of vascular structures and glands were observed within these two areas.④.The anterior macula flava was elliptical in shape in the horizontal position.Its maximum length and width were 2.78mm and 1.14mm respectively at the level of the juncture of the upper two fifths and lower three fifths of the vocal cords.The three-dimension spatial shape was an olive and was 1.87mm in height.The anterior macula flava is arranged from the anterior-internal to posterior-lateral(start from the cranial to the caudal).There were collagen fibers between the bilateral anterior maculae flavae.⑤.The vocal muscle was located at the medial aspect of the lateral laminae of the thyroid cartilage and connected to the intermediate lamina of the thyroid cartilage via the collagen fibers.Conclusions:①.Anatomically,the anterior commissure of the larynx is defined as an area located between the anterior portions of the vocal cords and extending laterally for approximately 3mm.The upper surface of the vocal cords is not only the upper boundary of the anterior commissure,but also the anatomic separation between supraglottic and glottic regions at the most anterior part of the larynx.②.The dense portions of the anterior commissure tendon and the anterior macula flava are located in the upper two fifths of the vocal cords and in the upper two thirds respectively,and comprise the barriers of the anterior commissure together.But they play the different roles in resistance to the vertical and horizontal spread of laryngeal tumors.They act together as a vertical barrier against the supraglottic tumors spreading inferiorly and the subglottic tumors spreading superiorly.In addition,the dense portion of the anterior macula fiava limits the spread of the tumors from one vocal cord to the opposite as a horizontal barrier.