CHAPTER XVL 



THE RESPIRATORY SYSTEM. 



This system comprises the nose, epiglottis, trachea, 

 larynx, bronchi, lungs and pleura. These tissues are 

 derived from the mesoderm and the epiderm. The 

 nerve supply is from the cerebro spinal and sympathetic 

 system. The epiglottis is chiefly yellow cartilage. Its 

 mucous surface is covered sparingly with taste buds. 

 The larynx is cartilagenous. The trachea is composed 

 of three coats : mucous, submucous and fibrous. The 

 mucous coat consists of ciliated epithelial cells, base- 

 ment membrane and elastic fibers. The submucous 

 coat consists of cartilage, glands, elastic tissue and non- 

 striated muscle. The cartilage is of the hyaline vari- 

 ety and is arranged in the shape of a horseshoe. "The 

 large bronchi are like the trachea in structure, only the 

 cartilage is not arranged in a loop, but is arranged in 

 plates." Sobotta. A bronchus having a diameter not 

 over I micron is called a bronchiole. They still have a 

 layer of muscle and a layer of cubic epithelial cells. 

 These bronchioles lead into the respiratory bronchioles, 

 (120) 



