Final answer:
During endochondral ossification, the formation of the cartilage model precedes all other events. This cartilage template is essential for the subsequent development of the primary ossification center, followed by vascular invasion and the formation of secondary ossification centers.
Step-by-step explanation:
The event that must precede all others during endochondral ossification is the formation of the cartilage model. This is the initial step in the process where mesenchymal cells differentiate into chondrocytes to form the future bony skeleton. This cartilaginous model serves as a template for new bone formation.
Following the establishment of the cartilage model, subsequent events occur in a specific sequence: capillaries penetrate the cartilage, the perichondrium transforms into periosteum, and then a primary ossification center develops within the diaphysis of the bone. As the process continues, secondary ossification centers eventually develop in the epiphyses of the bone.
Understanding the sequence of these events is critical because it reveals how bone develops and matures. It is important to note that during endochondral ossification, the primary ossification center appears prior to the vascular invasion and the formation of secondary ossification centers.