Question

Arrange the following events of endochondral ossification in proper sequence.

(1) A bone collar is formed and perichondrium becomes periosteum.
(2) Chondrocytes enlarge and cartilage is calcified.
(3) Cartilage model is formed.
(4) A secondary ossification center forms in the epiphysis.
(5) Blood vessels from the periosteum invade calcified cartilage and form the primary ossification center.
A) 3, 2, 1, 5, 4
B) 1, 2, 3, 4, 5
C) 3, 1, 2, 5, 4
D) 1, 3, 2, 4, 5

Answer 1

The correct sequence of events for endochondral ossification is when a cartilage model is formed, and finally, a secondary ossification center forms in the epiphysis, which is option A) 3, 2, 1, 5, 4.

Step-by-step explanation:

To arrange the following events of endochondral ossification in proper sequence, we must understand the step-by-step process through which bone tissue replaces hyaline cartilage. Here are the events in order:

1. Cartilage model is formed. Mesenchymal cells differentiate into chondrocytes, creating the cartilage model of the future skeleton.
2. A bone collar is formed and perichondrium becomes periosteum. Capillaries penetrate the cartilage, transforming the perichondrium into a bone-producing periosteum and forming a periosteal collar of compact bone around the diaphysis.
3. Chondrocytes enlarge and cartilage is calcified. As the matrix calcifies, it prevents nutrients from reaching the chondrocytes, leading to their death, and causing cavities to open in the cartilage.
4. Blood vessels from the periosteum invade calcified cartilage and form the primary ossification center. This invasion leads to modifications of the calcified cartilage matrix into spongy bone.
5. A secondary ossification center forms in the epiphysis. Following the development of the primary ossification center, secondary ossification centers appear in the epiphyses.

Considering the steps of endochondral ossification, the correct sequence is option A) 3, 2, 1, 5, 4.