398 



HEAD AND NECK 



the maxillary sinus. The upper boundary of the hiatus 

 semilunaris is prominent and bulging. It is termed the bulla 

 ethmoidalis. On or above the bulla is the aperture of the 

 middle ethmoidal cells (Fig. 156). The slit-like opening of 

 the maxillary sinus lies in the posterior part of the hiatus 

 semilunaris. 



The dissector should now open up the maxillary sinus by removing 

 its lateral wall. This may be done by sawing upwards through the root of 

 the zygomatic process of the maxilla. 



The orifice by means of which this great air sinus com- 



Orifice of anterior 

 ethmoidal cells 



Hiatus semilunaris 



Atrium 



Orifice of maxil- 

 lary sinus 



Vestibule 



Orifice of naso-lacrimal duct 



Frontal air-sinus 



Bulla ethmoidalis 



Orifice of middle ethmoidal cells 



Orifices of posterior ethmoidal cells 



Recessus spheno-ethmoidalis 

 Sphenoidal sinus 



Cut edge of 

 middle concha 



Middle meatus 



Lateral pharyn- 

 geal recess 



Orifice of 



auditory tube 



Salpingo- 



pharyngealfold 



Soft palate 



Inferior mealus 



Cut edge of inferior 

 concha 



FIG. 156. Lateral wall of Nasal Cavity and Naso-pharynx. The 

 three conchae have been removed. 



municates with the middle meatus lies in the medial wall 

 of the cavity much nearer the roof than the floor a position 

 highly unfavourable for the escape of fluids which may 

 collect in it. Sometimes, however, a second orifice, circular 

 in outline, will be found. This is situated lower down ; when 

 it is present it opens into the middle meatus, immediately 

 above the middle point of the attached margin of the inferior 

 concha. 



The dissector should note that, on account of the relationship of the 

 infundibulum to the hiatus semilunaris and of the latter to the opening 

 of the maxillary sinus, there is a tendency, in some cases, for the secretion 

 of the frontal sinuses to flow into the maxillary sinus. 



