Final answer:
At puberty, epiphyseal plates cease their growth as cartilage cells stop dividing and are replaced by bone, resulting in the epiphyseal plate transforming into the epiphyseal line and the fusion of the epiphysis and diaphysis.
Step-by-step explanation:
Changes in Epiphyseal Plates at Puberty
During puberty, the epiphyseal plates undergo significant changes as part of the bone development process. Some of these plates are associated with larger bones like the femur, which have multiple secondary ossification centers. As hormones regulate bone growth, chondrocytes in the epiphyseal plate eventually stop dividing, leading to the cessation of the cartilage proliferation that drives bone lengthening. Subsequently, the cartilage is replaced by bone, signaling the end of longitudinal growth. This replacement results in the transformation of the epiphyseal plate into the epiphyseal line in mature bone, marking the point where the epiphysis and diaphysis have fused. The appearance of this epiphyseal line indicates that the bone has reached its maximum length.
In long bones, growth ceases around age 18 in females and age 21 in males through a process called epiphyseal plate closure. These developmental changes are critical for understanding bone maturity and are often observed as differences in radiographic images, where plates appear dark due to their lower density compared to ossified bone.