84 



THE SKELETON 



in the recent state with mucous membrane and present numerous foramina for 

 blood-vessels and, above, grooves for twigs of the olfactory nerves. Each 

 concha has an attached upper border and a free, slightly convoluted, lower 

 border, and in the case of the middle concha, the lower margin has already been 

 noticed on the outer aspect, where it overhangs the middle meatus of the nose. 

 The posterior extremity of the labyrinth articulates with the anterior surface 

 of the body of the sphenoid and is commonly united with the sphenoidal concha. 



A rounded prominence on the lateral wall of the middle meatus is known as the bulla 

 ethmoidalis. Antero-inferior to the bulla is a large semilunar depression [hiatus semilunaris] 

 which corresponds to the lower aperture of the infundibulum. 



Manj' of the ethmoidal cells are imperfect and are completed by adjacent bones. Those 

 alons the superior edge of the lateral mass are the fronto-ethmoidal; those at the anterior 

 border, usually two in number, are known as lacrimo-ethmoidal. Those along the lower 

 edge of the lamina papyracea are the maxillo-ethmoidal; and posteriorly, are the spheno- 

 ethmoidal, completed by the sphenoidal concha, and a palato-ethmoidal cell. The anterior 

 extremity presents one or two incomplete cells closed by the nasal process of the maxilla. 



Blood-supply. — The ethmoid receives its blood-supply from the anterior and posterior 

 ethmoidal arteries and from the spheno-palatine branch of the internal maxillary. 



Articulations. — ^With the frontal, sphenoid, two palate bones, two nasals, vomer, two 

 inferior nasal conchae, two sphenoidal conchae, two maxillae, and two lacrimal bones. The 

 posterior surface of each labyrinth is in relation with the sphenoid on each side of the crest and 

 rostrum, and helps to close in the sphenoidal sinus. 



Ossification. — -The ethmoid has three centres of ossification. Of these, a nucleus appears 

 in the fourth month of intra-uterine hfe in each labyrinth, first in the lamina papyracea and 

 afterward extending into the middle concha. At birth each lateral portion is represented by 

 two scroll-like bones, very dehcate and covered with irregular depressions, which give it a worm- 

 eaten appearance. Six months after birth a nucleus appears in the ethmo-vomerine cartilage lor 

 the vertical plate which gradually extends into the crista galli, and the cribriform plate is formed 

 by ossification extending laterally from this centre, and medially from the labyrinth. The 

 three parts coalesce to form one piece in the fifth or sixth year. 



The ethmoidal cells make their appearance about the third year, and gradually invade 

 the labyrinths. In many places there is so much absorption of bone that the cells perforate 

 the ethmoid in situations where it is overlapped by other bones. Along the lower border, near 

 its articulation with the maxilla, the absorption leads to the partial detachment of a narrow 

 strip known as the uncinate process. Sometimes a second but smaller hook-like process is 

 formed, above and anterior to this, so fragile that it is difficult to preserve it in disarticulated 

 bones. The relations of the uncinate process are best studied by removing the lateral wall of 

 the maxillary sinus. 



THE INFERIOR NASAL CONCHA 



The inferior nasal concha (inferior turbinate) (fig. 105) is a slender, scroll-like 

 lamina, attached by its upper margin to the lateral wall of the nasal fossa, and 

 hanging into the cavity in such a way as to separate the middle from the inferior 



Fig. 105. — The Inferior Concha, Adult Sphenoidal Turbinate, and Lacrimal Bones. 



The crest of lacrimal 

 Tensor tarsi 

 The orbital surf • 



Lacrimal gr> 



Hamular process — 

 Conchal process 

 The lacrimal process 

 The ethmoidal process 



The maxillary process 



The sphenoidal concha with an 

 orbital process 



Middle nasal concha 



meatus of i\u\ nose. It may l)o regarded as a dismemberment of the ethmoidal 

 labyrinth, with which it is closely related. It presents for examination two 

 surfaces, two borders, and two extremities. 



The lateral surface is concave, looks toward the lateral wall of the nasal fossa, 



I 



