THE INFERIOR TURBINATED BONES. 135 
THE INFERIOR TURBINATED BONES. 
The inferior turbinated or spongy bone (concha inferior) is a shell-like lamina 
of bone lying along the lower part of the outer wall of the nasal fossa. Of 
elongated form, the bone displays two curved borders enclosing an internal and 
external surface. 
The superior or attached border is thin and sharp in front and behind, where 
it articulates with the inferior turbinal crests on the inner surface of the body 
of the superior maxilla and the vertical plate of the palate bone, respectively. 
Between these two borders the central part of the upper edge rises in the form of 
a sharp crest, the fore part of which forms the upstanding lachrymal process (pro- 
cessus lachrymalis), which articulates above with the descending process of the 
lachrymal bone, as well as with the edges of the nasal groove of the superior 
maxilla, thus completing the osseous canal of the nasal duct. The posterior end 
of this crest is elevated in the form of an irregular projection called the ethmoidal 
process (processus ethmoidalis). This unites with the uncinate process of the 
ethmoid bone (see Fig. 98). Spreading downwards from the middle of the 
superior border, on its outer side, is a thin irregular plate of bone, the maxillary 
process (processus maxillaris), which partially conceals the outer concave surface 
Lachrymal process Ethmoidal process Lachrymal process 
Md f_—Ethmoidal process 
wt 
Maxillary process 
A B 
Fic. 106.—RicHt INFERIOR TURBINATED Bone. A, Inner Surface ; B, Outer Surface. 
of the bone, and, by its union with the inner wall of the maxillary sinus, assists in 
the completion of the partition which separates that cavity from the inferior nasal 
meatus. The inferior or free border, gently curved from before backwards and 
slightly out-turned, is rounded and full, and formed of bone which is deeply pitted 
and of a somewhat cellular character. The anterior and posterior extremities of 
the bone, formed by the convergence of the upper and lower borders, are thin and 
sharp; as a rule the hinder end is the more pointed of the two. The internal 
surface projects into the nasal fossa; convex from above downwards, and slightly 
eurved from before backwards, it forms the floor of the middle meatus. It is 
rough and pitted, and displays some scattered and longitudinally directed vascular 
grooves. The outer surface overhangs the inferior nasal meatus. Concave from 
above downwards, and to some extent from before backwards, it is directed towards 
the outer wall of the nasal fossa. It is smooth in. front, where it corresponds to 
the opening of the canal for the nasal duct; behind and towards its lower border, 
it is irregular and pitted. In the disarticulated bone, this surface is in part con- 
cealed by the downward projecting maxillary process. 
Connexions. — The inferior turbinal articulates with the superior maxilla, lachrymal, 
ethmoid, and palate bones. 
Variation.—A case in which the inferior turbinals were absent has been recorded by 
Hyrtl. 
Ossification. — The inferior turbinate bone, the maxillo-turbinal of comparative 
anatomy, is derived from the cartilage forming the outer wall of the nasal capsule, the 
upper portion of which forms the ethmo-turbinals. It ossifies, however, from a separate 
centre, which appears about the fifth month of foetal life, and later contracts a union 
by a horizontal lamella on its outer side with the superior maxillary bone. 
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