260 ANATOMY FOR NURSES [Chap. XIV 



Molars are twelve in number in the permanent set, but there 

 are only eight in the temporary set. 



The molars, or true grinders, have broad crowns with small, 

 pointed projections, which make them well fitted for crushing and 

 bruising the food : they each have two or three roots. The twelve 

 molars do not replace the temporary teeth, but are gradually 

 added with the growth of the jaws ; the last or hindermost molars 

 may not appear until twenty-one years of age; hence called 

 " late teeth " or " wisdom teeth." 



Function. — The teeth assist in the process of mastication by 

 cutting and grinding the food. 



THE PHARYNX 



The pharynx, or throat cavity, is a musculo-membranous bag 

 shaped somewhat like a funnel, with its broad end turned upward, 

 and its constricted end downward to end in the oesophagus. 

 It is about four and a half inches (113 mm.) long, and lies behind 

 the nose and mouth. Above, it is attached to the base of the 

 skull, and behind, to the cervical vertebrae ; in front and on each 

 side are apertures which communicate with the nose, ears, mouth, 

 and larynx. 



Of these apertures there are seven : — 



Two in front above, leading into the back of the nose, the 

 posterior nares. 



Two, one on either side above, leading into the Eustachian 

 tubes, which communicate with the ears. 



One midway in front, the fauces. 



Two below, one opening into the larynx and the other into the 

 oesophagus. 



The mucous membrane lining the pharynx is well supplied 

 with glands, and at the back of the cavity there is a con- 

 siderable mass of lymphoid tissue. During infancy and child- 

 hood this may increase to such an extent that it interferes with 

 nasal breathing. The child is then said to have adenoids and 

 is obliged to breathe through the mouth ; hence the term " mouth 

 breathers." 



Function. — The muscular tissue in the walls of the pharynx is 

 of the striped variety, and when the act of swallowing is about to 



