Endochondral ossification Anatomy

Endochondral Ossification

 Endochondral/cartilaginous ossification

Endochondral/cartilaginous ossification is the process of formation of bone from the preformed cartilaginous model (premature long bone).

• The process of bone formation begins in the centre of the shaft of a long bone. This site where bone formation begins is called the primary ossification centre. This centre forms the diaphysis.
• Later, ossification centres appear at different intervals at each end of the cartilaginous model. These are called secondary ossification centres. These centres form the epiphyses.
• The hyaline cartilage plate separating the epiphysis and diaphysis is called epiphyseal plate/growth plate. It is essential for the growth of bone in length.
• When the epiphysis unites with the diaphysis, the epiphyseal plate is replaced by a linear scar called the epiphyseal line.

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Epiphysis: Definition & Anatomy

Question 1. Define ossification and ossification centres.
Answer.

Ossification is the process of bone formation.

Ossification centre The ossification centres are sites where bone formation begins.

There are two types of ossification centres:

1. Primary and
2. Secondary.
3. Primary centre: It appears before birth in the centre of the shaft or body of bone which it forms.
4. Secondary centre: It appears later, usually after birth at each end of the bone which it forms.

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Question 2. What are the different types of epiphyses?
Answer.

There are four types of epiphyses:

1. Pressure epiphyses: They are present at the ends of long bones. They are, therefore, articular in nature and take part in the transmission of weight, for example, the head of the femur, lower end of the radius and medial end of the clavicle.
2. Traction epiphyses: They are nonarticular in nature and are not involved in the transmission of weight. They provide attachment to one or more muscle tendons, which exert traction on it, for example, greater and lesser trochanters of the femur, and greater and lesser tubercles of the humerus.
3. Atavistic epiphyses: Phylogenetically, they represent a separate bone, which in man has become fused secondarily to another bone, for example, the coracoid process of the scapula, posterior tubercle of the talus (os trigonum).
4. Aberrant epiphyses: They are not always present but appear sometimes, for example, epiphysis at the head of the 1st metacarpal.