Final answer:
The epiphyseal plate, a layer of hyaline cartilage found in the metaphysis area, separates the epiphysis from the diaphysis in juvenile long bones and is responsible for their lengthwise growth until early adulthood.
Step-by-step explanation:
Understanding the Epiphyseal Plate in Juvenile Long Bones
In juvenile bones, the region that separates the epiphysis from the diaphysis is known as the epiphyseal plate, also commonly referred to as the growth plate. This layer of transparent hyaline cartilage plays a crucial role in the lengthwise growth of long bones. The epiphyseal plate is found within the metaphysis, a narrower area at the junction of the epiphysis and diaphysis.
During bone growth, new cartilage is continually being produced on the epiphyseal side of the plate, while older cartilage is ossified on the diaphyseal side, contributing to the bone's increase in length. In the structure of a typical long bone, spongy bone fills the epiphysis and is responsible for the production of red blood cells in the red bone marrow. The epiphyseal plate is eventually replaced by osseous tissue, forming an epiphyseal line when the bone has finished growing in early adulthood (around ages 18-21).