Trachea (1 of 2)View from just below the vocal cords. Note the u-shaped cartilaginous tracheal rings that give the trachea some firmness and resistance to collapse. The membranous third of the circumference puts a flat "lid" on the trachea, but can bulge inward when a person coughs. Trachea (2 of 2)View from the middle of the trachea in a different patient. Here the tracheal rings are shaped more like an “o” but the top of the “o” is completed by the membranous tracheal wall marked by the blue line. Also, the carina is seen distally and marked by an "x". This is where the trachea divides into right and left mainstem bronchi. [Gallery not found]Trachea (1 of 1)Radiographic view at the upper chest level. The horseshoe-shaped anterior segment of the trachea’s wall, two-thirds of the total circumference, is the trachea’s cartilaginous component. The posterior one-third is the membranous trachea, which also constitutes the anterior one-third of the esophagus, and is also called the tracheoesophageal party wall. The esophagus is dilated with air; this patient has undergone a total laryngectomy. Mild tracheobronchopathia osteochochondroplastica (1 of 2) A milder expression of this disorder. This person has been followed for years for a different problem, so these are incidental findings. Across the years, there has been no change in the lesions seen here in the trachea.