OPENING INTO THE (ESOPHAGUS. 661 



aperture is unobstructed, but in the act of deglutition it is closed 

 by the approximation of the lateral folds and the lower part of the 

 epiglottis. 



The OPENING INTO THE (ESOPHAGUS (o) IS the narrowest part of Beginningof 



the pharynx, and is opposite the cricoid cartilage and the sixth ""' 

 cervical vertebra. At this spot the mucous membrane in the 

 oesophagus becomes paler than in the pharynx ; and the point at 

 which the pharynx ends is marked externally by a slight contraction, 

 and by a change in the direction of the muscular fibres. 



The CAVITY OF THE PHARYNX is divided into three parts, which Subdivision 

 differ in their function with regard to the transmission of the food phJJJi? ' 

 and air. The upper or nasal portion is limited below by the soft illto nasal > 

 palate and its posterior pillars ; it gives passage only to air, and is 

 always open. The middle or oral portion extends downwards to oral, 

 the aperture of the larynx, and is traversed by both food and air ; 

 it is open when breathing through the mouth, but closed when 

 breathing solely through the nose, the aperture of the larynx then 

 corresponding to the interval between the posterior pillars. The 

 third part being behind the larynx is termed laryngeal, and only and laryn- 

 truhsmits food ; its walls are naturally in contact, except during the fions P r ~ 

 act of deglutition. 



The SOFT PALATE (velum pendulum palati ; Q) is a moveable Soft palate 

 structure between the mouth and the pharynx, which can either niouth: 

 close the opening of the mouth, or cut off the communication with 

 the nose, according as it is depressed or elevated. In the usual surfaces ; 

 position of the soft palate (the state of relaxation) its anterior 

 surface is concave, and is continuous with the roof of the mouth ; 

 while the opposite surface is convex and turned to the pharynx. 

 The upper border is fixed to the posterior margin of the hard borders ; 

 palate ; and on each side it joins the pharynx. The lower border from it 

 is free, and is produced in the centre into a conical pendulous part 

 the uvula (p). Along its middle is a slight ridge, indicative of 

 the original separation into two halves. 



Descending from the soft palate on each side of the fauces are Arches or 

 the two folds of mucous membrane before referred to, containing pl 

 muscular fibres, and named the arches or pillars of the soft palate 

 or fauces. The anterior pillar (i) springs from the anterior surface anterior; 

 of the soft palate near the base of the uvula, and reaches to the 

 side of the tongue rather behind the middle ; and the postei*wr (L), posterior, 

 longer than the other, is continued from the lower border of the 

 velum to the side of the pharynx. As they diverge from their 

 origin to their termination, they limit a triangular space in which 

 the tonsil lies. 



The soft palate consists of an aponeurosis, wish muscles, vessels, Consti- 

 nerves, and mucous glands ; and the whole is enveloped by the velum, 

 mucous membrane. 



Dissection. Some of the muscles of the palate are readily Dissect 

 displayed, but others require care in their dissection. 



The two principal muscles of the soft palate the elevator and levatorand 



tensor on 

 right half; 



