GENERAL HISTOLOGY

Detailed explanation-1: -Cells on the inner surface of the periosteum differentiate into osteoblasts and secrete osteoid parallel to that of the existing matrix, thus forming layers. These layers are collectively called the compact/cortical bone [2].

Detailed explanation-2: -The osteoblasts form a collar of compact bone around the diaphysis. At the same time, the cartilage in the center of the diaphysis begins to disintegrate. Osteoblasts penetrate the disintegrating cartilage and replace it with spongy bone. This forms a primary ossification center.

Detailed explanation-3: -1. Spongy bone tissue begins to develop at sites within the membranes called centers of ossification. 2. Red bone marrow forms within the spongy bone tissue, followed by the formation of compact bone on the outside.

Detailed explanation-4: -Intramembranous Ossification. During intramembranous ossification, compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue. The flat bones of the face, most of the cranial bones, and the clavicles (collarbones) are formed via intramembranous ossification.