552 ANATOMY IN A NUTSHELL. 



tweeD the superior turbinated bone and middle turbinated bone at the upper 

 and back pari of tin- nasal fossa. This meatus occupies the posterior one-third 

 of the outer wall of the nasal fossa. The spheno-palatine foramen opens into 

 it at the back part of its miter wall, while the posterior ethmoidal cells open into 

 it at the anterior part of the outer wall. The spheno-ethmoidal recess is be- 

 hind the superior turbinated bone at the superior and posterior part of the 

 nasal fossa and opens into the sphenoidal sinus. 



The middle meatus occupies the posterior two-thirds of the outer wall of 

 the nasal fossa and is situated between the middle turbinated bone and the 

 inferior turbinated bone. This meatus communicates anteriorly with the 

 anterior ethmoidal cells by means of the infundibulum and through these cells 

 with the frontal sinus. The opening of the antrum of Highmore is near the 

 center of this meatus. 



The inferior meatus, which is the largest of the meatuses, is situated be- 

 tween the inferior turbinated bone and the floor of the nasal fossa. It will 

 be noticed that the superior meatus occupied the posterior one-third of the 

 outer wall and the midlle meatus occupied the posterior two-thirds of the 

 outer wall, while the inferior meatus occupiesthe entire length of the outerwall 

 of the nasal fossa. The canal for the nasal duct opens at the anterior extremity 

 of this meatus. 



The nasal fossae extend from the base of the cranium to the roof of the 

 mouth, and are situated on each side of the middle line of the face. They are 

 two large cavities which are separated from each other by a thin septum. The 

 anterior nares open on the front of the face from the nasal fossa' while the pos- 

 terior nares open into the pharynx. The frontal sinus communicates with 

 the nasal fossa above, the sphenoidal sinus communicates with the nasal fossa 

 posteriorly, and the antrum of Highmore and the ethmoidal sinus communi- 

 cate with it externally. The orbit is joined to the nasal fossa by the lachry- 

 mal groove. The mouth communicates with the nasal fossa by the anterior 

 palatine canal. The cranium communicates with the nasal fossa by the ol- 

 factory foramina, and the spheno-maxillary fossa communicates with the nasal 

 fossa by the spheno-palatine foramen. Sometimes the nasal fossae communi- 

 cate with each other by an opening in the septum. There are fourteen bones 

 in the nasal fossae. They include all the bones of the face except the two malar 

 and the inferior maxillary, and in place of these three it has the frontal, eth- 

 moid and sphenoid of the crainum. The ethmoid bone with all its articu- 

 lation- make the nasal fossa-. The frontal, ethmoid, and sphenoid are com- 

 mon to the nasal fossa, cranium and the orbits. 



There are numerous foramina at the base of the skull extending from the 

 foramen csecum to the foramen magnum. There are also three large fossae at 

 the base of the skull, namely, the anterior fossa, middle fossa, ami the posterior 

 fossa. (Plate CCXXXV.) 



Till. WTI.imu; FOSSA HAS THE FOLLOWING FORAMINA: 



1. Foramen caecum through which a vein passes to the superior longitu- 

 dinal sinus, sometimes one from the frontal sinus. This is a single foramen, 

 while the others in this fossa arc in pair-. 





