Secondary ossification center Secondary ossification centers are found at the epiphyses of long bones. This process is similar to that of the primary center of ossification, but occurs without a bone collar. Instead, osteoprogenitor cells enter the epiphyseal cartilage, differentiate into osteoblasts, and secrete matrix on the cartilage framework.
How many ossification centers does the calcaneus have?
The calcaneus has two ossification centers: the first appears during gestation, the second at about 10 years. The second epiphysis fuses with the main bone at about 20 years. The talus will develop a second center that does not join the main body of the bone; this is called an os trigonum.
What does the combined ossification center fuse to?
Ossification. This combined ossification center fuses to the lateral epicondyle at the same time to form the main body of the distal humeral epiphysis. The epiphysis fuses to the metaphysis of the humerus as early as 12 to 13 years of age, which signals the end of longitudinal growth of the distal humeral physis.
When does the ossification of the talus occur?
The ossification of the talus and calcaneus begins before birth, while the process in the navicular does not begin until 3 years in males and 2 years in females. Except for the calcaneus, each of the bones of the hindfoot ossifies from one center, which appears during the fetal period.
What is the process of intramembranous ossification?
Intramembranous Ossification This process involves the direct conversion of mesenchyme to the bone. It begins when neural crest-derived mesenchymal cells differentiate into specialized, bone-forming cells called osteoblasts. Osteoblasts group into clusters and form an ossification center.
What is the zone of ossification and calcification?
Zone of calcification – Calcium ions brought to the epiphysis through blood vessels calcify the cartilage matrix surrounding the dying chondrocytes. Although it is calcified, this is not yet bone tissue. Zone of ossification – In this zone, osteoprogenitor cells arrive and become osteoblasts.
