Abstract
In order to clarify the development of vascular structures during formation of the secondary palate, vascular patterns in the palate were studied three dimensionally in normal and vitamin A treated Wistar rats by india ink perfusion and resin cast preparation.
The results are summarized as follows.
1. The vascular plexus of the palatal shelves before reorientation was denser in the oral side than in the nasal side in both normal embryos of 15.5 days gestation and cleft embryos of 16.5 days gestation. T h e findings indicate that different proliferative activities in the two regions resulting from different bl o od supply may contribute to the reorientation of the palatal shelves.
2. In the normal group the vascular plexus of the palatal shelves during the period of medial extension were stretched laterally, possibly because vascular regeneration could not catch up with the rapid growth o f the palatal shelves. On the other hand, such chasges were not observed in the cleft group in which the palat a l shelves showed no growth toward the midline.
3. In the normal group, many small spherical masses were observed along the medial edge of palatal vascular plexus in the resin cast preparations of the palatal shelves just before and during f usion, indicating that some change has taken place in the capillary wall before forming anastomosis.
4. In both groups, dense vascular distribution was observed in the area of bone formation to meet active osteogenesis.
5. Compared to the normal group, reorientation of the palatal shelves and formation of the maxilla were delayed by 1 to 1.5 days in the cleft group.
6. Although ultimate development of the vascular structure was attained in the cleft group, vascular development was delayed and was associated with alterations in the microvascular structure such as the thickness of capillary vessels and the density of vascular plexus.
