Document DM7eQg6gbLp0dwmg1L4ON6DwM

362 0. A. SANDER fibrosis, usually not disabling, but there may be marked disability when emph; sema is advanced and fibrosis is massive and progressive. 7. Beryllium (beryllium oxide): Generalized granulomatosis. Marked di ability when largely pulmonary because of interalveolar edema and fi-brosi Probably a sensitivity response and not a true'-pneumoconiosis. Berylliosis. Other dusts, which are not of interest here because of not being retainers! the lungs, are those that may cause chemical irritation of the upper respirat" mucous membrane, such as acids, alkalies, fluorides, chromates, cadmium, nicll carbonyl, and so forth. Many dusts inhaled into the lungs (lead, manganese, a5 so forth) are completely absorbed by the blood and may cause systemic poisonif Many dusts, principally those that are organic, are purely allergens and may cail asthma and hay fever. Others, such as zinc oxide and cotton, may cause transitor, chills and fever. III. Anatomical Factors of Importance in Injury by Dust The fate of inhaled dust in the body can be understood only by knowing som thing of the anatomical structures and physiological reactions involved jif respiration. The air passageway consists of the nose, pharynx, trachea, bronchi, bronch'i oles, and alveoli. The relationship of these various structures is shown in Figured 1. Nose. The portions of the nasal cavities just within the external nares ar lined with skin containing hairs. The remaining parts of the nasal cavities & lined with" mucous membrane, composetf on its surface of ciliated and mujj* secreting cells. This tissue is highly vascular and contains freely, anastomojsi venous channels. The nasal passages are connected directly with the air sinii in the skull. The hairs in the entrance of the nose and the mucous material secreted by|* lining membrane collect many of the larger inhaled particles. The cilia of the A respiratory tract tend to move material toward the mouth, those of the noseflf ing to force the mucous and particles in it toward the pharynx. The important;' the nose as a protective mechanism has been indicated by G. Lehmann.6 T investigator studied 426 miners, of whom 241 had silicosis and 181 were norma and found the median, efficiency of nasal filtering in the silicotics to be 27.blW cenTancTm'the normals per cent. He" concluded'from "this that p^rponapm develop silicosis do so, impart at least, because of a faulty filtering mechani|^i the nose. ' Z. Pharynx. The pharynx is a common pathway for food and air, connect! nasaLpassagarffiiliiithemM^pathw.ay_and_with-the-traGheaj;ts-nasal-p6ttlf'' lined with ciliated epithelium. S. Larynx and trachea. The larynx lies between the pharynx and trachea^ L. E. Hamlin, Rocky Ml. Med. J., 41, 391 (June, 1944). G. Lehmann, Arbeitsphysiol, 7, 147 (1933); see also J. Ind. Hyg., 17, 37 (1935) PULMONARY DUST DISEASES 363