Final answer:
New cartilage is formed at the growth plates of long bones and during embryonic development through the process of endochondral ossification. Secondary ossification centers also contribute to cartilage formation post-birth. Cartilage growth is essential for bone lengthening in childhood and also plays a role in bone healing after injuries.
Step-by-step explanation:
New cartilage is primarily formed in areas called growth plates or epiphyseal plates, which are found at the ends of long bones. During embryonic development, the process of endochondral ossification begins with areas of mesenchyme transforming into hyaline cartilage, which serves as a model for future bone formation. The primary ossification center forms in the middle of this cartilage during fetal development, starting the process of bone formation. Over time, the secondary ossification centers develop, usually after birth, in the epiphyseal regions. Chondrocytes, which are cartilage-producing cells, are responsible for the continued growth of cartilage at the ends of the bones, facilitating the lengthening of bones during childhood and adolescence.
In cases of bone injury, an internal callus of fibrocartilaginous matrix and an external callus of hyaline cartilage and bone are formed by chondrocytes and osteoblasts, which stabilizes the fracture. This cartilage is eventually replaced by bone through endochondral ossification as part of the healing process.