Textbook of normal histology: including an account of the development of the tissues and of the organs . reaching the small bronchi the epithelium is reduced toa single layer of ciliated columnar cells. The thickness of themucosa at first is not greatly diminished, since the loss sustained inthe thinning of the elastic tissue of the tunica propria is compensatedby the appearance of an additional layer of non-striped musclesituated at the outer border of the mucosa, next the submucosa ; thislayer, which corresponds to a muscularis mucosae, forms a com-plete investment, especially conspicuous wh
Textbook of normal histology: including an account of the development of the tissues and of the organs . reaching the small bronchi the epithelium is reduced toa single layer of ciliated columnar cells. The thickness of themucosa at first is not greatly diminished, since the loss sustained inthe thinning of the elastic tissue of the tunica propria is compensatedby the appearance of an additional layer of non-striped musclesituated at the outer border of the mucosa, next the submucosa ; thislayer, which corresponds to a muscularis mucosae, forms a com-plete investment, especially conspicuous when the cartilaginous platesdiminish. The ring-cartilages of the bronchi become reduced insize, then broken up, and finally replaced by irregular short plates ;these, becoming smaller and infrequent, embrace gradually less ofthe circumference of the tube, until in the bronchial twigs of thediameter of about one millimetre they altogether disappear. By repeated division the bronchial tubes become greatly reducedin size, the reduction being accompanied by the changes already THE RESPIRATORY ORGANS. 251. Section of portion of bronchus of child : a, epithelium; b,basement-membrane; c, stroma of mucosa; d, layer of in-voluntary muscle; e, submucosa ; /, acini of mucous glands ;h, blood-vessels ; i, obliquely cut duct of mucous glands. noted ; when the diameter of the twig no longer exceeds one milli-metre the tube is termed a terminal bronchus ; Fig. 286. these divisions open intothe somewhat larger al-veolar passages, thewalls of which are besetwith air-sacs, and fromwhich extend blind ir-regular or pyramidalspaces, the infundi-bula; each infundibu-lum is surrounded on allsides by the air-sacs,which communicatefreely with the formercavity, but not directlywith each other. Greaterexactness suggests ad-ditional subdivisions ofthe alveolar duct intovestibule, atrium, and infundibular passage (Miller). The walls of the terminal bronchial tubes consist at first of asingle layer of ciliat
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Keywords: ., bookauthorpiersolgeorgeageorgea, bookcentury1800, bookdecade1890
