An electron microscopic study of the human fetal mandibular periosteum.

The authors studied the submicroscopic structure of the human fetal periosteum. The mandible was in the 4 ..5th month of the fetal life formed of woven bone. The periosteum consisted of the cambial and fibrous layers. The cambial layer contained active osteoblasts, characterized by numerous endoplasmic reticulum profiles, flat cells with signs of osteolytic activity in their surroundings, and cells anchored to the bone matrix by their processes. From these cells the osteocytes developed. The submicroscopic structure of the young osteocytes was similar to that of osteoblasts. The fibrous layer contained numerous collagen fibres and fibroblasts, which were in the resting or active metabolic state. The results and literature are discussed in the paper.