Growth of Cartilage Model

Soon after its construction, the hyaline cartilage model is infiltrated by blood vessels. The nutrients supplied by these blood vessels change previously inactive cells into osteoblasts and the process of ossification truly begins.

In long bones, such as those found in the arms and legs, this process begins in the centre of the hyaline cartilage in what is known as the primary ossification centre. Here the cartilage is calcified. This cuts off the nutrient supply to the matrix, which begins to deteriorate leaving cavities in the newly formed bone. This would lead to a weakness if it were not for the simultaneous development of a bone collar around the outside of the cartilage.

Development of Cartilage Model

The starting point for this type of bone growth is the hyaline cartilage model, which acts in a similar way to the membranes involved in the early process of intramembranous ossification giving an initial shape to the developing bone.

Medullary Cavity Formation

Calcification in the centre of the bone pushes the osteoblasts to either end where they continue their work causing the diaphysis (shaft) to grow in length. The diaphysis is made up of hard (compact) bone.

Growth of Cartilage Model

Soon after its construction, the hyaline cartilage model is infiltrated by blood vessels. The nutrients supplied by these blood vessels change previously inactive cells into osteoblasts and the process of ossification truly begins.

In long bones, such as those found in the arms and legs, this process begins in the centre of the hyaline cartilage in what is known as the primary ossification centre. Here the cartilage is calcified. This cuts off the nutrient supply to the matrix, which begins to deteriorate leaving cavities in the newly formed bone. This would lead to a weakness if it were not for the simultaneous development of a bone collar around the outside of the cartilage.

Development of Primary and Secondary Ossification Centres

Osteoblasts are also responsible for the formation of the epiphyseal or growth plates, which are found at either end of the bone and separate the diaphysis from the epiphyses. The epiphyses are generally larger, more expanded sections of spongy (cancellous) bone, which are covered with a thin layer of articular cartilage. This section essentially works to absorb the shock produced by movement.

Medullary Cavity Formation

Calcification in the centre of the bone pushes the osteoblasts to either end where they continue their work causing the diaphysis (shaft) to grow in length. The diaphysis is made up of hard (compact) bone.

Formation of the Articular Cartilage and Epiphyseal Plate

The epiphyseal or growth plates, as the name suggests, are slowly responsible for the continuing growth in length of bones after birth. As well as containing osteoblasts, they also contain osteoclasts that break down bone. The combination of these two types of cell ensures that bones grow at the correct rate, in the correct shape and with the correct percentage of compact the cancellous bone.

Development of Primary and Secondary Ossification Centres

Osteoblasts are also responsible for the formation of the epiphyseal or growth plates, which are found at either end of the bone and separate the diaphysis from the epiphyses. The epiphyses are generally larger, more expanded sections of spongy (cancellous) bone, which are covered with a thin layer of articular cartilage. This section essentially works to absorb the shock produced by movement.