Bones of the Cranium. 



11 





9. Ethmoid Bone, Os e 

 moideum, from the outside. 



10. Ethmoid Bone; perpen 

 dicular plate. 



ihmot dales 



11. Ethmoid Bone; inner surface of the labyrinth. 



The ethmoid bone is divided into: 1. cribriform plate, 

 Lamina crilrosa ; 2. perpendicular plate, Lamina perpmdicularis ; 

 3. and 4. the cellular lateral masses, the ethmoidal laby- 

 rinths. 



The cribriform plate is divided into 2 halves by the Crista 

 ctlimoidalis, which, projecting upward, forms the Crista galli. The cribri- 

 form plate is perforated by the Foramina cribrosa. From its under sur- 

 face the perpendicular plate (Fig. 10), which forms the upper 

 part of the bony Septum narium, decends. 



The labyrinth (Fig. ll) is divided into the ethmoidal cells, 

 Cdlulae ethmoidales (anterior, middle and posterior) , which are closed 

 externally by the Lamina papyracea (Os planning - internally they are 

 limited by the superior and inferior ethmoidal t u r b i n a t e d 

 bones, Concha ethmoidalis superior et inferior, between which lies the 

 superior meatus _of the nose, Meatus narium superior. 



From the anterior end of the inferior ethmoidal turbinated bone (middle 

 turbinated bone), and from the lower walls of the anterior ethmoidal cells, 

 there projects the thin, serrated unciform process, Processus uncinatus. 



The ethmoid bone articulates with 15 bones; with 4 cranial bones, 

 the sphenoid, the 2 sphenoiclal turbinated i. e. Ossicula Bertini, the frontal, and 

 11 bones of the face; the 2 nasal bones, 2 superior maxillary, 2 lachrymal, 

 2 palate, 2 inferior turbinated, and the vomer. 



