Endochondral Ossification
Written by Shrishti Harish
Endochondral Ossification is the primary method by which most of the bones in the body form. The mesenchymal skeleton turns into a cartilage model and finally bone. After this step, a cartilage model grows in length and width. Bones start to form when the cartilage stops growing.
The first step of this fascinating process is the development of the Cartilage Model. This is executed by replacing the mesenchymal skeleton. Additionally, chondroblasts (cartilage) and perichondrium (periosteum) develop. During this step, a bony collar starts to form. However, it is formed through intramembranous ossification and helps with the growth of the cartilage model. Once the model is developed, it grows in length and width. In scientific terms, it is called interstitial and appositional growth.
Blood vessels move into the cartilage model and form the primary ossification center. The primary ossification center is the center region of the model in which vasculature moves in through nutrient foramina. Nutrient Foramina is a vast channel that provides the cartilage model with nutrient arteries.
The fourth step of EO is the development of the Medullary Cavity. Osteoclasts (bone-breaking cells) work to break down the cartilage model. They also eradicate bones associated with the primary ossification center. A secondary ossification site starts to develop around birth and vasculature moves towards the extremities of bones. The extremities are called epiphyseal vasculatures and are crucial for supplying blood to the growth plates, enabling proper bone growth.
Last but not least is the formation of articular cartilage and epiphyseal lines. These structures assist in maintaining joint function and bone integrity. Articular Cartilage provides a cushion that absorbs impact during movement, whereas the epiphyseal lines transition from growth to maturity in long bones.
References
https://www.kenhub.com/en/library/anatomy/bone-tissue-formation
https://open.oregonstate.education/aandp/chapter/6-4-bone-formation-and-development/
Written by Shrishti Harish from MEDILOQUY