ABSTRACT
In the human respiratory tract, the submucosa consists of glands and cartilage, the two occurring together, with the gland mainly internal to the cartilage lying between it and the epithelium but also between the plates of cartilage. Glands are most numerous in the trachea, progressively decreasing distally, along with the cartilage. Almost all the tools and methods available for morphological experimental research in other tissues have also been applied to tracheobronchial gland studies. Methods of morphologically estimating or quantifying tracheobronchial gland size or volume have been developed to investigate chronic obstructive pulmonary disease, particularly chronic bronchitis. Secretory cells in tracheobronchial submucosal glands consist of mucous and serous cells that contain secretory granules. High-iron diamine staining with the ultrastructural level has also demonstrated three different zones with granule profiles in some mucous cells in rat trachea. Morphometric analyses of secretory cell granules in submucosal glands have been performed at both light and electron microscopic levels.
