THE NASAL FOSS^ 



111 



The roof is horizontal in the middle, but sloped downward in front and behind. The 

 anterior slope is formed by the posterior surface of the nasal bone and the nasal process of the 

 frontal; the horizontal portion corresponds to the cribriform plate of the ethmoid and the sphe- 

 noidal concha; the posterior slope is formed by the inferior surface of the body of the sphenoid, 

 the ala of the vomer, and a small portion of the sphenoidal process of the palate. The sphe- 

 noidal sinus opens at the upper and back part of the roof into the spheno-ethmoidal recess, 

 above the superior meatus. 



The floor is concave from side to side, and in the transverse diameter wider than the roof. 

 It is formed mainly by the palatine process of the maxilla and completed posteriorly by the hori- 

 zontal part of the palate bone. Near its anterior extremity, close to the septum, is the incisive 

 canal. 



The septum or medial wall is formed by the perpendicular plate of the ethmoid, the vomer, 

 the rostrum of the sphenoid, the crest of the nasal bones, the frontal spine, and the median 

 crest formed by the apposition of the palatine processes of the maxillae and the horizontal 

 parts of the palate bones. The anterior border has a triangular outline limited above by the 

 perpendicular plate of the ethmoid and below by the vomer, and in the recent state the defi- 

 ciency is filled up by the septal cartilage of the nose. The posterior border is formed by the 



Fig. 136.- 



-Section through the Nasal Fossa to show the Lateral Wall with 

 THE Meatuses. 



Superior nasal concha 



Probe in sphenoidal foramen 



Sphenoidal sinus 

 Sella turcica 



Superior meatus 



Spheno-palatine 



foramen 



Middle nasal 

 concha 



Uncinate process of ethmoid 



Internal pterygoid plate 



Palate bone 



Probe in posterior palatine canal 



Probe in naso- 

 lachrymal canal 



Frontal sinus 



Bristle in the 

 infundibulum 



Nasal bone 



—Agger nasi 



Lachrymal bone 

 Lower end of bristle 

 in middle meatus 

 Middle meatus 



Inferior nasal 

 concha 



Probe at lower end 

 of naso -lachrymal 

 canal where it 

 opens into inferior 

 meatus 



Incisive canal 



pharvngeal edge of the vomer, which separates the two choanse. The septum, which is usually 

 deflected from the middle hne to one side or the other, is occasionally perforated, and m some 

 cases a strip of cartilage, continuous with the triangular cartilage, extends backward between 

 the vomer and perpendicular plate of the ethmoid (posterior or sphenoidal process). 



The lateral wall is the most extensive and the most comphcated on accomit of the forma- 

 tion of the meatuses of the nose. It is formed by the frontal process and the medial surface of 

 the maxilla, the lacrimal, the superior and inferior conchse of the ethmoid, the mferior nasal 

 concha, the vertical part of the palate bone, and the medial surface of the medial pterygoid 

 plate. The three concha, which project medially, overhang the three recesses known as the 

 meatuses of the nose. The superior meatus, the shortest of the three, is situated between the 

 superior and middle nasal concha;, and into it open the orifice of the posterior ethmoidal cells 

 and the spheno-palatine foramen. The middle meatus hes between the middle and inferior 

 conchje. At its fore part it communicates with the frontal sinus by means of the infundibulum, 

 and near the middle with the maxillary sinus (antrum) ; the communication with the sinus is 

 very irregular and sometimes represented by more than one opening (fig. 136). Two sets of 

 ethmoidal cells— the middle and anterior— also open into the middle meatus, the anterior in 

 common with the infundibulum, the middle on an elevation known as the bulla ethmoidahs. 

 The inferior meatus, longer than either of the preceding, is situated between the inferior nasal 

 concha and the floor of the fossa, and presents, near the anterior part, the lower orifice ot the 

 canal for the naso -lacrimal duct. 



