Csontképzdés

Csontképződés, also known as ossification or osteogenesis, is the process by which bone tissue is formed. This is a vital process that begins during embryonic development and continues throughout life, albeit at a slower pace. There are two primary mechanisms by which bone is formed: intramembranous ossification and endochondral ossification.

Intramembranous ossification occurs directly from mesenchymal connective tissue. This process is characteristic of the formation of flat bones, such as those of the skull, and the clavicles. Mesenchymal cells differentiate into osteoblasts, which secrete osteoid, the unmineralized extracellular matrix of bone. This osteoid then mineralizes, and the osteoblasts become trapped within lacunae, differentiating into osteocytes.

Endochondral ossification, on the other hand, involves the replacement of a hyaline cartilage model with bone tissue. This is the primary method for the formation of long bones, vertebrae, and the bones of the limbs. A cartilage model is first formed, which is then invaded by blood vessels and osteoblasts. The cartilage is gradually broken down and replaced by bone. This process continues at the epiphyseal plates of long bones until skeletal maturity, allowing for bone lengthening.

Throughout life, bone remodeling, a continuous process of bone resorption by osteoclasts and bone deposition by osteoblasts, ensures bone strength, repair of microdamage, and adaptation to mechanical stress.