DEGLUTITION. 155 



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the process of deglutition, which occurs in three stages. 

 The first stage includes the passage from the mouth into 

 the pharynx. The food being collected into a heap on the 

 tongue, the tip of that organ is placed against the front of 

 the hard palate, and then the rest of the tongue is raised 

 from before back, so as to compress the food mass between it 

 and the palate and drive it through the fauces. This much 

 of the act of swallowing is voluntary, or at least is under 

 the control of the will, although it commonly takes place 

 unconsciously. The second stage of deglutition is that in 

 which the food passes through the pharynx; it is the most 

 rapid part of its progress, since the pharynx has to be 

 emptied quickly so as to clear the opening of the air-pas- 

 sages for breathing purposes. The food mass, passing back 

 over the root of the tongue, pushes down the epiglottis ; at 

 the same time the larynx (or voice-box at the top of the 

 windpipe) is raised so as to meet the epiglottis, and thus 

 the passage to the lungs is closed.* The soft palate is, at 

 the same time, moved into a horizontal position, so as to 

 separate the upper (or respiratory) portion of the pharynx, 

 leading to the nose and the Eustachian tubes (see Fig. 41), 

 from its lower portion, which ends inferiorly in the gullet. 

 Finally the isthmus of the fauces is closed as soon as 

 the food has passed through, by the contraction of the 

 muscles on its sides, and the elevation of the root of the 

 tongue. All passages out of the pharynx except the gullet 

 being thus blocked, when the pharyngeal muscles contract 



Describe the first stage. What is the second stage? Which 

 stage is most rapid? Why? How is the passage to the lungs 

 closed while food is passing through the pharynx? How is the 

 passage to the nose blocked? Describe the processes of the second 

 stage of deglutition. 



* The raising of the larynx during swallowing can be readily felt by placing 

 the finger on its large cartilage forming "Adam's apple" in the neck. 



