THE RESPIRATORY SYSTEM 



313 



0.5 mm. From the small interlobular bronchi are given off the ter- 

 minal bronchi. These are respiratory in character and are described 

 with the lungs. 



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Fig. 210. — Transverse Section of Small Bronchus from Human Lung. X115. (Tech- 

 nic 2, p. 32^.) a, Stroma; b, epithelium; c, muscularis mucosae; d, fibrous coat. 



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^5!*--i- 



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<«-'^. 



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Fig. 211 . — Transverse Section through small Bronchus of Human Lung. (Sobotta.) 

 Simple columnar ciliated epithelium; no cartilage; no glands; mucosa folded longitudi- 

 nally; elastic tissue stained with Weigert's elastic tissue stain. 



In studying the bronchi it is convenient to arbitrarily divide them into large, 

 medium-sized, and small bronchi. 



Large bronchi have essentially the same structure as the trachea except for 

 somewhat thinner walls. 



Medium-sized bronchi (Fig. 2c8) have an epithelium about three layers deep, 

 disconnected plates of cartilage, a continuous layer of smooth muscle disposed 

 circularly as a muscularis mucosae, and tubular glands 



