Final answer:
The epiphyseal plate, also known as the growth plate, is the layer of hyaline cartilage that enables lengthwise growth of long bones during development. It is eventually replaced by bone to form the epiphyseal line when growth ceases.
Step-by-step explanation:
The epiphyseal plate is a layer of hyaline cartilage found in the metaphysis of a growing bone. This growth plate is critical in endochondral ossification, a process by which bone is formed by replacing hyaline cartilage. The epiphyseal plate facilitates the lengthwise growth of long bones, consisting of four zones, each with specific cellular activities that contribute to bone elongation. On the epiphyseal side, cartilage is formed, while on the diaphyseal side, this cartilage is ossified, allowing the diaphysis to grow in length. This plate remains until adolescence, after which it is replaced by bone tissue and fuses to form the epiphyseal line, marking the end of bone growth in length.
The periosteum surrounds the outer surface of the bone and is the interface for attachment of tendons and ligaments. The epiphyseal plate's functioning ends once it has completely ossified, resulting in a fused adult bone—a stage known as synostosis.