[Histological studies of the mouse palate. Formation of the incisive suture]

The morphology of the incisive suture (InS) in mice was studied using specimens stained with alizarin red S. Formation of this suture was also studied histologically with light microscopy. The InS is composed of three regions; the 1st and 2nd are short and well interdigitated regions respectively situated on the inside and the outside of the anterior palatine foramen. The 3rd region is a loose curved region situated on the outside and the nasal cavity side of the cranium. The InS surrounds the posterior region of the incisors in the upper jaw with a ring-like form. The InS is formed in four steps; cell aggregation (19 days postconception and one day postpartum), formation of bone extensions and collagen fiber bundles (4 and 7 days postpartum), modification of the orientation of these fiber bundles (14 days postpartum), and formation of the serrated suture and fiber bundles with regular orientation (21, 30 and 60 days postpartum). Furthermore, the distance between the bones in the InS was found to be from 40 to 60 microns. The morphology of the InS indicates that it functions as a strong connection between bones, and as a buffer zone. These functions of the InS seem to correspond closely with the function of the incisors in the upper jaw.