CHAPTER XVI. ANATOMY OF THE SEPTUM.-DEVIATION OR III. The two nasal passages are separated by a median wall common to both-the septum. This is made up in front and below of the quadrangular cartilage, in its upper portion of the vertical plate of the ethmoid bone, while its inferior posterior part is the vomer. The extreme anterior tip is membranous and consists of skin. A dense perichondral membrane covers the cartilage underneath the mucous membrane, while the bony plates have a periosteal lining. In its upper anterior region the mucous membrane is thickened into a tumefaction-the tuberculum of the septum-rich in glands and veins. Some distance above the floor the mucous membrane forms a series of shallow ridges during development, which usually dwindle later on, but sometimes enlarge in hypertrophic rhinitis (Fig. 60). During its early fetal formation the septum is a single plate of cartilage reaching from floor to roof. About the second month the vomer becomes differentiated in the form of two ossifying parallel plates, joined in front, below, and behind, but including between them the original cartilaginous layer. Toward birth these two bony plates coalesce, with disappearance of the included cartilaginous plate.. At the upper border, however, the bony plates are still separated by a groove in which a strip of cartilage persists. By this time the vertical plate of the ethmoid, too, has ossified from above downward, and now joins the upper border of the vomer, leaving still the strip of cartilage now incased by bony walls. This condition may change to complete ossification during adult life, or may persist indefinitely. 112. The developed vomer represents a stout bony lamella, the height of which increases from before backward, by reason of the slope of its upper or anterior border. Its inferior border articulates with a narrow ridge at the median junction of the two superior max FIG. 60.-Nasal septum after detachment of its mucous lining: L, Perpendicular plate of the ethmoid; V, V, vomer; Q, quadrangular cartilage; S, nasal spine of the frontal bone; C, nasal crest of the palate bone (Zuckerkandl). illary and the two palatal bones, reaching thus from the front to the rear end of the floor of the nose. The sloping anterior border connects partly with the quadrangular cartilage, and back of it with the vertical plate of the ethmoid. It runs up to the rostrum or spine on the inferior surface of the sphenoid, where it turns to form the short (superior) border articulating with the rostrum. The posterior free edge of the vomer slants upward and backward and is concave. The quadrangular cartilage articulating in front and above with the nasal bones forms the median wall of the external nose. The triangular cartilaginous plates of the sides of the nose are joined to it. Its inferior anterior rounded corner is framed by the short, thick, membranous septum, which thus completes the middle wall of the external nose. The inferior border of this cartilage rests. on the anterior half of the vomer. At this contact the edges of cartilage and bone are sometimes square; more often, however, the cartilaginous edge is bent toward one side and overlaps the bony junction, or is split overriding the bone on both sides, while the vomer may or may not have its groove obliterated. These irregularities of the junction are the starting-point of morbid crests. The vertical plate of the ethmoid completes the gap between the roof of the nose, the anterior surface of the sphenoid bone, the upper border of the vomer, and the cartilaginous septum. septum. The ossification of this bony lamella proceeds from above downward and extends forward to a variable extent, so that while the bridge of the nose is mostly supported by this bony plate, it rests occasionally only on the cartilaginous septum. The ossification is completed by the sixth year, at the latest about the ninth year of life. But, as before described, a strip of cartilage usually remains after this. period, for a variable length of time, incased by bony walls--viz., by the inferior edge of the vertical ethmoid plate and the trough formed by the upper border of the vomer. The lateral crests so often found in the nose are due to hypertrophy of this cartilaginous remnant, with secondary bulging of the sides of the bony trough. 113. The normal septum is not always an ideal straight wall. Asymmetry due to curvature is found in more than one-half of all skulls of the white races. In uncivilized tribes septum deviations occur only to the extent of about 25 per cent. The deflection pertains principally to the cartilaginous portion, but may involve, to a variable extent, the perpendicular part of the ethmoid plate. The deflected septum is convex and bulging toward one side and correspondingly concave on the other. The curvature is usually more marked in the vertical than in the horizontal plane. The convexity may be scarcely noticeable, or may, on the other hand, occlude practically the one nasal passage. Sometimes a double S-shaped bend is met with, reducing the patency of both sides. When the asymmetry extends to the front portion of the septum, the external nose is deflected to one side. Occasionally, but not often, the free anterior end of the cartilage is deflected and then usually thickened, so as to occlude partly one side of the vestibule (Fig. 61). The architecture of an asymmetric septum is very often complicated by the existence of lateral FIG. 61. Stenosis of the right nostril by thickening and deflection of the anterior end of the septal cartilage. The membranous septum is displaced to the left, and thereby narrows the left nostril. crests on one or even both sides, which thicken it and augment its injurious mechanical influence. Regarding the causes of asymmetry of the septum, many unfounded hypotheses have been recorded. But nothing more positive can be stated than that it is the result of a disproportionate growth of the septum as compared with that of the rigid bony frame within which it is contained. In very pronounced cases of curvature it is sometimes apparent that the concavity of the septum corresponds to the smaller maxillary bone, which has not attained the growth of its mate, giving the entire face an asymmetric expression. Pronounced asymmetry is rarely observed before the second dentition. The influence of traumatism, so often quoted, has been much overrated. It does seem in some instances to lead to an exaggeration of a preexisting asymmetry, but it is scarcely probable that it can cause a deflection without fracture of a previous straight septum. 114. Less frequent, but clinically more important, than deviations of the septum are the lateral crests, also called spurs and septal ridges or spines. They occur in about every third skull and are often associated with some deflection. The lateral crests are protuberances on 138 FIG. 62.-Frontal section through the nose, showing a large crest on the left side of the septum: a, a, Septum; b, crest (Zuckerkandl). the side of the septum in the form of ledges running backward and somewhat upward. They begin usually in the cartilaginous portion, but sometimes only at the bony part, and may or may not extend up to the sphenoid bone. In the cartilaginous portion they may or may not be double-sided. In the bony part they are, as a rule, one-sided, and if bilateral, one is much more prominent than the other. These protuberances may be |