[Histogenesis and three-dimensional observation on condylar cartilage in prenatal mice]

The present investigation is carried out to study the histogenesis and the three-dimensional interrelationship of the mandibular condyle, mandibular body, angular cartilage and Meckel's cartilage in the C57BL mouse fetuses. The frontal serial sections obtained at 13 to 18 days of gestation (plug day = 0) were used for the histological observation and the digitized area data from the tracings of each specimen were provided for the computer-aided reconstruction. The results were as follows: 1. The primordium of the condylar cartilage appeared in the area of the superio-lateral site of the primordium of the mandibular body at 14.5 days of gestation. 2. After 14.5 days of gestation, the mandibular body developed, covering the primordium of the condylar cartilage, but its developmental process was slightly different between the medial and the lateral site. 3. The condylar cartilage at 16 days of gestation was comparable to carrot-shape. 4. Endochondral bone formation was demonstrated at the most medial portion of the condylar cartilage at 18 days of gestation.