Distribution of tracheal and laryngeal mucous glands in some rodents and the rabbit

We used scanning electron microscopy to count the number of mucous gland op enings in the tracheae and lower portion of the larynges of the rat, guinea pig, hamster, mouse and rabbit. Cells of the airway surface epithelium wer e removed by protease digestion better to visualise the gland openings. The distribution of glands was further studied by conventional histology and b y PAS/Alcian blue staining of whole mounts. In all rodent species, gland op enings in the larynx occurred with a frequency of 1-2 per mm(2). Mice had n o gland openings in their tracheae, and hamsters, only a handful. Rat trach eae contained 126 +/- 42 gland openings (+/-S.D.; n = 6) at a frequency of similar to 0.6 per mm(2) at the top of the trachea and similar to 0.15 per mm(2) at the bottom. Guinea pig tracheae contained 153 +/- 90 gland opening s (+/- S.D.; n = 5), with 54 % being in the top 40 % of the trachea. In bot h rat and guinea pig, tracheal glands were found in the ventral aspect betw een the cartilaginous rings, and were absent from the dorsal membranous por tion. Gland openings in most species were simple circles of similar to 50 m um diameter. However, glands in the rat trachea generally opened obliquely into shallow (similar to 20 mum deep) oval troughs (similar to 150 x 75 mum ), which had their long axes oriented from head to tail. In the rabbit, the re was no evidence of tracheal or laryngeal glands histologically. However, the tracheal and laryngeal surfaces contained numerous pits (similar to 30 mum diameter) distributed evenly over and between cartilages at a frequenc y of similar to 4 per mm(2). These may correspond to the 'nests' of goblet cells described by others.