Investigations on the growth pattern of the maxillary sinus in Japanese human fetuses.

The growth pattern of the maxillary sinus was analyzed using 18 human fetuses of both sexes between 9 and 21 weeks of age postconception. The paraffin embedded specimens were cut in series in the frontal and the transversal plane, respectively. The inner surface of the maxillary sinuses was redrawn and surrounded with a digitizer and then the volumes were calculated. A correlation analysis as well as a simple linear regression analysis between the values of the maxillary sinus, different linear values of the nasal cavity and the crown-rump length (CRL) served to prove possible growth relations. The maxillary sinus' Anlage was already identifiable in the 29.8 mm (CRL) fetus. From this first appearance, the maxillary sinus expands not only in posterior direction but also in anterior direction from 11 weeks onwards. The maxillary sinus volume increased from 0.0008 mm3 at the age of 9 weeks to more than 9 mm3 at the age of 21 weeks. The results of the statistical analysis indicated, that the relationship between the maxillary sinus' Anlage and the nasal cavity were strongly influenced by the body size (CRL). This study suggests, that the growth of the maxillary sinus follows special regularities in the early fetal development.