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)