any structural anomaly of the tubuloacinar seromucous glands located principally in the submucosa of the trachea whose excretory ducts pass through the lamina propria to the tracheal lumen; they secrete mucus, lysozyme, defensins, and other agents that help protect the lungs from particles and infectious agents; in the mouse, they are restricted to the upper trachea, more specifically to the regions between the first few cartilage rings, with the precise distribution depending on genetic background