150 



The Vertebrate Organ Systems 



The main nasal passageway is divided into two halves by the nasal 

 septum. Into each passage a series of bones, the conchae, project. 

 These are covered with a thin, ciliated mucous membrane. In the upper 

 portion of each passage is a patch of ciliated olfactory epithelium, the 

 odor receptors. Air entering the body is thus constantly sampled for 



FROnTAL AIR sinus 



SUPERIOR 

 TURBinATE 



MIDDLE 

 TURBINATE 



IMFERIOR 

 TURBItlATE 



ETHMOID AIR CELt 



(TN^SELLA TURCICA 



SPHEnOlO AIR 



smus 



EUSTACHIAN TUB£ 



TORUS TUBARIUS 



SOFT PALATE 



MYLOHYOID 

 MUSCLE 



THYROID CARTILAGE 

 VOCAL CORD 

 TRACHEA 



L-.: ' ESOPHAGUS 



Fig. 44. — A sagittal section of the upper portion of the respiratory tract. 

 (From Zoethout and Tuttle: Textbook of Physiology.) 



possibly unpleasant or even dangerous odors. In man this sense plays 

 a role of much less importance than among many other mammals. The 

 cilia on the mucous membranes serve to remove dust particles from the 

 entering air, while this same air is warmed and humidified during its 

 passage over these membranes. 



The sinuses of the skull have their lining mucous membranes con- 

 tinuous with those of the nasal passages. They communicate with these 



