Prenatal growth of the human vomeronasal organ.

BACKGROUND: Vomeronasal organs (VNOs) are paired epithelial structures located adjacent to the nasal septum that form in the late first trimester of human fetal development. Although VNOs have long been known to exist in fetal and adult humans, some studies continue to suggest that these structures may be degenerative or functionless. Little is known of the growth of the VNO. METHODS: The present study examined length and volume changes of the human VNO in 26 "normal" (10 female, 16 male) histologically prepared fetuses from the University of Pittsburgh and the University of Michigan across three trimesters (8-30 weeks postmenstrual age). A computer reconstruction technique was used to quantify lengths and volumes of right and left VNOs, and regression equations were generated to assess growth rates. RESULTS: A linear increase in VNO length and a logarithmic increase in VNO volume with increasing postmenstrual age was found. Volume increase was noted for both the vomeronasal epithelium and the lumen of the VNO. A comparison with most estimates of adult human VNO length suggested that further prenatal or postnatal size increase occurs. The growth curves also suggested a more rapid growth in VNO length and volume for females than for males. CONCLUSIONS: The present study demonstrates that the fetal human VNO commences volumetric increase in the early second trimester but does not achieve maximum size during fetal development. Further investigation is needed to determine whether the human VNO is sexually dimorphic in size.

Formation and enlargement of the paranasal sinuses in normal and cleft lip and palate human fetuses.

OBJECTIVE: Comparisons of paranasal sinus morphology between humans with and without cleft lip and palate (CLP) have yielded conflicting opinions regarding size differences. Although postnatal samples have been investigated, no studies have compared paranasal sinus volumes between cleft and noncleft human fetuses. METHOD: The nasal cavities of 20 'normal' and 9 CLP human fetuses (8-21 weeks' postmenstrual age) were examined to assess prenatal volumetric changes of the maxillary sinuses, anterior and posterior ethmoidal air cells, and sphenoidal sinuses. Lengths and volumes of right and left maxillary and sphenoidal sinuses were calculated from histologically prepared sections using a computer reconstruction technique, and regression equations were generated to assess the enlargement rates. RESULTS: All paranasal sinuses were found among both normal and CLP specimens in the same locations and in similar age ranges. However, greater shape asymmetry was noted for all sinuses in CLP compared to normal specimens. In the normal sample, results indicated significant (p < .05) correlations between right or left maxillary sinus length (R2 = 0.49, 0.54) and volume (R2 = 0.67, 0.68), and increasing postmenstrual age, but no significant (p > .05) correlations were observed for right or left sphenoidal sinus length or volumes and postmenstrual age. Maxillary sinus length changes were best described by second-order polynomial regression equations, and volume changes were best described by logarithmic equations. When individual right or left sinuses of CLP specimens were compared to the mean of the normal sample, one maxillary sinus was significantly (p < .05) larger, and 9 maxillary sinuses were not significantly (p > .05) different. Sphenoidal sinus lengths and volumes of CLP specimens were within the same range compared to these dimensions for the normal sample. CONCLUSION: Results on normal specimens indicate that maxillary sinuses exhibit second-trimester length and volume increases, whereas sphenoidal sinuses are more variable. This study suggests a similar timing of sinus formation in normal and CLP fetuses, but shape asymmetries are frequently detected among CLP specimens. In particular, the sphenoidal sinuses may be altered in shape and size by adjacent, hypertrophic cartilaginous structures in CLP fetuses. These results indicate that the maxillary sinuses of CLP fetuses are not deficient in size compared to noncleft fetuses.

Vomeronasal organ growth and development in normal and cleft lip and palate human fetuses.

As part of an ongoing investigation of normal and cleft lip and palate (CLP) fetal midfacial development, the vomeronasal organ (VNO) was examined in 35 human fetuses (26 normal and 9 CLP) ranging in age from 8 to 30 weeks postmenstrual age. All specimens were examined histologically, and a computer reconstruction technique was used to quantify lengths and volumes of right and left VNOs and anterior paraseptal cartilages (PCs). Growth curves were generated for these data and were compared between normal and cleft samples. VNOs and PCs were present in all normal fetuses, whereas VNOs were found in only 5 of 9 CLP specimens and PCs were found in 8 CLP specimens. The side of the palatal cleft in specimens with unilateral CLP was associated with PC dysmorphologies but appeared to have no influence on VNO presence or absence. Septal dysmorphologies were observed in most CLP specimens with absent or abnormal VNOs. VNO length increased in a linear fashion across ages, and VNO volume was seen to change in a logarithmic fashion. Individual CLP specimens did not differ significantly from the mean of the normal sample for VNO length or volume. PC length was seen to change in a sigmoidal fashion, and PC volume changes were best described by a logarithmic curve. In contrast to findings on the VNO, CLP specimens exhibited significantly different growth rates (line slopes) for PC length and volume compared to the normal sample. Results on the normal sample suggested that the human fetal VNO exhibits volumetric increases between the 16th and 30th weeks of development, but this increase begins later and proceeds more slowly than that of the PCs. Examination of the CLP sample suggested that the VNOs were of "normal" size for age, but may be vulnerable to septal dysmorphologies that result in altered location or disruption.

Anterior paraseptal cartilage development in normal and cleft lip and palate human fetal specimens.

As part of an ongoing study of age-related variation in fetal cleft lip and palate nasal capsule morphology, anterior paraseptal cartilage development was examined histologically in a sample of nine complete cleft lip and palate human fetuses, and 20 without clefts ranging in age from 8 to 21 weeks. A computer reconstruction technique was used to quantify lengths, volumes, and generate growth curves from various regression equations. Anterior paraseptal cartilage length was seen to change in a sigmoidal fashion while volume changes were best described by a logarithmic curve for both groups, with the steepest increases from 15 to 21 weeks. Cleft specimens exhibited significantly different growth rates (line slopes) for both length and volume dimensions compared with the normal specimens. The larger, for age, cartilages were associated with an enlarged, inferior border of the nasal septal cartilage and vomer in the cleft sample. These results are consonant with previous findings in this cleft fetal sample of other enlarged midline structures (i.e., nasal septal cartilage and vomer). Results suggest that growth abnormalities in one or all of these structures may be yet another mechanism for early nasal airway impingement and reduction in cleft lip and palate neonates.

Growth rate of the vomer in normal and cleft lip and palate human fetal specimens.

The present study, part of an ongoing investigation of normal and dysmorphic development of the human fetal oronasal capsule, examined the rate of growth of the vomer. For comparative purposes, 29 human fetal specimens (20 "normal" and 9 cleft lip and palate [CLP]) were celloidin embedded, sectioned, stained with hematoxylin and eosin, and serially digitized. The specimens ranged from 8 to 21 weeks in postmenstrual age. The application of a well-documented three-dimensional reconstruction technique provided quantification of several aspects of the vomer. CLP vomer length and volume were growing at a faster rate in the 8 to 21 week age range. Growth curves were produced by plotting length and volume against postmenstrual age and a significant difference was noted between the slopes (growth rate) of the linear component of the normal and CLP growth curves for vomer length (p less than .001) and volume (p less than .001). This study tested the hypothesis of a more rapidly growing 8 to 21 week CLP vomer and observed that the growth trends of the CLP vomer are similar to those of the CLP nasal septum, which also was found to possess a significantly larger (p less than .001) volumetric growth rate throughout the course of the vomer. Comparative findings suggest that a pathogenetic correlate of CLP is the rapid enlargement of the midline structures of the oral and nasal capsules.

Size and growth rate of the tongue in normal and cleft lip and palate human fetal specimens.

In the present study, the size and rate of growth of the tongue was assessed in human fetuses. For comparative purposes, 29 human fetal specimens (20 "normal" and 9 with cleft lip and palate were celloidin embedded, sectioned, stained with hematoxylin and eosin, and serially photomicrographed. The specimens ranged from 8 to 21 weeks postmenstrual age. The application of a well documented three-dimensional reconstruction technique provided quantification of several aspects of the tongue. Tongue length and volume were larger in the cleft specimens than for the normal specimens, while both length and volume were growing at a faster rate. Growth curves were produced by plotting length and volume against postmenstrual age and a significant difference was noted between the slopes (growth rate) of the growth curves for tongue length and volume for the two groups. Tongue length increase was approximately 2.27 times greater and tongue volume increase was approximately 1.64 times more for the cleft specimens than for the normal specimens from 8 to 21 weeks. In support of these findings, tongue volume was relatively larger expressed as a contribution of total oronasal capsule volume in the cleft specimens. For an initial age category (8 to 12 weeks), tongue volume in the cleft specimens was larger, growing at a faster rate than normal tongue volume and a significant difference was noted between the slopes of the growth curves. No significant difference was observed between the tongue length indices in the initial or the 8 to 21 week age category.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related morphologic differences in the components of the eustachian tube/middle ear system.

The current study utilized a three-dimensional computer graphics technique to analyze the size, shape, and positional associations of the eustachian tube (ET) cartilage and lumen, the levator veli palatini (LVP) muscle, and the tensor veli palatini (TVP) muscle. Older specimens 7 years and above (n = 13) were compared to young specimens less than 7 years (n = 4). Our results suggest that changes in ET function associated with age could result from size and shape differences in the ET cartilage and changes in the position of the LVP and TVP muscles.

Image recognition and the reconstruction of cleft palate histological preparations: a new approach.

Serial coronal histological sections of cleft palate and normal 12 week fetal specimens are video scanned. The digitized data in a matrix of 10(8) data points are recorded and through computer manipulation three dimensional reconstructions are produced. These can be resectioned by computer in various planes to expose any given structure for study. This is the first application of such a technique to these problems.