ANATOMICAL AND PHYSIOLOGICAL TACTORS 71 



extent, upon the rich blood and nerve supply with which it is 

 endowed. The coughing- rotlex, depending as it does upon a nerv- 

 ous mechanism, aids at times in the elimination of contaminated 

 material. 



Bloomfield* (1922) suggests that there are six factors of })ossiblc 

 importance in the elimination of bacteria from the respiratory 

 tract. These factors he enumerates as follows: "(a) anatomic 

 conditions; (b) the flushing mechanisms; (c) 1)actericidal action 

 of the secretions; (d) reactions of secretions: (e) the antagonistic 

 action of the indigenous flora toward invaders; and (f) phago- 

 cytosis." He calls attention to the importance of the swallowing 

 reflex as a protective mechanism and cites experiments showing 

 that the tonsils are subjected to very little exposure to bacteria con- 

 tained in the food or fluids entering the mouth. 



On the other hand, air currents entering the nose impinge imme- 

 diately upon the mucous membranes. A large number of bacteria 

 present in dust particles or in infectious droplets are arrested very 

 near the anterior nares. Those that succeed in passing this bar- 

 rier are caught in the mucous film covering the nasal membranes 

 and swept toward the pliarynx and esophagus by the cilia of the 

 epithelium. 



Located in the upper respiratory tract is also the tonsillar ring 

 consisting of the faucial tonsils, lingual tonsils, and adenoid tissue. 

 The latter is located in the dome of the nasophar^Tix and is struc- 

 turally lymphoid tissue. Since the tonsils contain many crypts in 

 which bacteria may find lodgment, it is not surprising that they 

 are frequently the site of acute or clu^onic inflammation. Like all 

 lymphoid tissue they contain along with lymphocytes other white 

 cells that are phagocytic. 



Directly associated witli the upper respiratory tract and com- 

 municating with it are certain otlier structures, for the most part 

 lined with the same kind of pseudostratified epithelium as that 

 covering the nose. These sti-uctures include the ethmoid, sphenoid, 

 frontal, and maxillary sinuses, as well as the middle ear and con- 

 junctiva. The lacrimal secretions are mildly germicidal and also 

 aid in the mechanical removal of bacteria. 



Should bacteria enter the sinuses they would become entangled 

 in the mucous film which is propelled to the opening of the ducts 



•Bloomfield, A. L. : Am. J. M. Sc. 104: S.^4, 1922. 



