476 THE RESPIRATORY SYSTEM. 



% 



The Lungs and Bronchi. 

 The Bronchi. 



HEMORRHAGE. 



In haemorrhage from the bronchi the source of the blood is often to 

 be sought in the parenchyma of the lung (see page 445) or in a ruptured 

 aneurism. But haemorrhage from the bronchial walls may occur in 

 tuberculous or other forms of ulceration, chronic bronchitis, malignant 

 tumors, etc. 



INFLAMMATION. (Bronchitis.) 



Acute Catarrhal Bronchitis. This is frequently associated with a simi- 

 lar process in the trachea. It is characterized by hypersernia and swelling 

 of the mucous membrane with the formation of exudate, which usually 

 consists largely of mucus formed by the hypersecretion of the mucous 

 glands or degeneration of the epithelial cells. Mingled with this are 

 exfoliated and more or less degenerated epithelium from the mucous 

 membrane, leucocytes from the dilated vessels of the subrnucosa, varying 

 numbers of red blood cells, and bacteria. 



The microscopic appearances differ in different parts of the bronchial 

 tubes in accordance with the differences in structure. Mucous glands, 

 when these are present, may reveal great functional activity, and their 

 ducts may be distended with mucus which, often mingled with exfoli- 

 ated and degenerated cells, streams out upon the surface. Swelling and 

 proliferation of the connective -tissue cells and endothelium of the vessels 

 of the submucosa, oedema, and emigration from the dilated vessels are 

 often marked. The leucocytes may be seen making their way through 

 the epithelium into the other exudates upon the surface. The epithelium 

 may be loosened, single or clustered cells falling off here and there, or 

 shreds of cells may exfoliate together (see Fig. 261). The deeper sphe- 

 roidal epithelia, the so-called mother cells from which the new ciliated 

 cells on the surface are formed in both physiological and pathological 

 regeneration, usually remain in place upon the basal membrane. In the 

 small bronchi whose walls are thin, little else may be seen than an irreg- 

 ular exfoliation of the epithelium. On the other hand, the smaller 

 bronchi may be much involved and their lumina filled with exudate ; 

 when this, which has been called "capillary bronchitis," occurs, the 

 inflammatory process usually involves the adjacent and associated terri- 

 tories of lung tissue, constituting one of the important forms of broncho- 

 pneumonia. In some forms of bronchitis the exudate may consist 

 largely of pus. 



Atelectasis of corresponding tracts of the lung may follow the occlu- 

 sion of the bronchi with exudate. As recovery advances, the submu- 



