Endochondral ossification is the process of bone formation from a model of cartilage.

Endochondral ossification is indeed the process of bone formation from a cartilage model. Here are the steps involved:

1. Development of Cartilage Model: Mesenchymal cells gather together in the area of future bones and differentiate into chondroblasts, which form the cartilage model.

2. Growth of Cartilage Model: Chondroblasts secrete extracellular matrix and proliferate, causing the cartilage model to grow.

3. Development of Primary Ossification Center: Nutrients can no longer reach the chondrocytes in the center of the cartilage model. These cells die and disintegrate, leaving cavities. Blood vessels invade these cavities, bringing osteoblasts that start to form spongy bone in the primary ossification center.

4. Development of the Medullary (Marrow) Cavity: Osteoclasts break down some of the newly formed spongy bone, creating a marrow cavity.

5. Development of Secondary Ossification Centers: These occur in the epiphyses (ends) of the bone. Blood vessels invade the epiphyses, bringing osteoblasts that form spongy bone. Unlike the primary ossification center, the spongy bone remains and no marrow cavity is formed.

6. Formation of Articular Cartilage and the Epiphyseal Plate: Hyaline cartilage on the ends of the bone becomes the articular cartilage. The remaining cartilage left between the primary and secondary ossification centers becomes the epiphyseal plate (growth plate).

This process continues until the entire bone is formed and only the articular cartilage and the epiphyseal plates remain as cartilage. The epiphyseal plates will continue to create new cartilage, which is replaced by bone, allowing the bone to grow in length until adulthood.