Endochondral Ossification

Growth And Development General Principles And Concepts

Question 1. Write a short note on endochondral ossification.
Answer. Endochondral bone formation deposits the bone at places where high levels of compression are present. So mostly it occurs in all movable joints and cranial bases.

Procedure

• Mesenchymal cells condense at the area of bone formation.
• Some of the mesenchymal cells get differentiated into chondroblasts and start to lay down the hyaline cartilage.
• As the differentiation of cartilage cells moves towards the metaphysic, cells organize into longitudinal columns which are subdivided into the following zones:
  • Reserve zone: It is the area that is closest to the epiphyseal end of the plate and consists of small chondrocytes inside the matrix.
  • Proliferative zone: This is the next layer towards the diaphysis and has stacks of slightly large chondrocytes. This makes new chondrocytes through mitosis and replaces dead chondrocytes at the diaphyseal end of the plate.
    • Zone of maturation and hypertrophy: Chondrocytes inside the next layer are larger and older than those that lie in the proliferative zone.
    • Zone of calcified matrix: Most of the chondrocytes that lie in this zone are dead as the matrix around them gets calcified. Both capillaries and osteoblasts from diaphysis penetrate this zone and osteoblasts secrete the bony tissue on remaining calcified cartilage.

Read And Learn More: Orthodontics Question And Answers

• Hyaline cartilage is surrounded by a membrane known as perichondrium. The perichondrium is highly vascular and consists of osteogenic cells.
• Intercellular substance that surrounds the cartilage cells get calcified because of the activities of the enzyme alkaline phosphatase which is secreted by cartilage cells.
• So now nutrition to the cartilage cells gets cut off which results in their death and there is the formation of empty spaces known as primary areolae.

Endochondral Ossification

• Blood vessels and the osteogenic cells from perichondrium invade the calcified cartilaginous matrix which looks like bars or walls because of the eating of the calcified matrix. This left out empty spaces between the walls known as secondary areolae.
• Osteogenic cells from perichondrium become the osteoblasts and arrange at the surface of bars of the calcified matrix.
• Osteoblasts now lay the osteoid which becomes calcified to form the lamellae of bone. Another layer of osteoid is secreted and this goes on and on. Now calcified matrix of cartilage acts as a support system for bone formation. In this manner endochondral ossification takes place.

Importance of Endochondral Ossification

• Cartilage acts as a soft tissue and growth occurs both by interstitial and appositional growth.
• Growth of cartilage can occur in heavy-pressure areas, as this is a pressure-adapted tissue, unlike the bone. Example is cranial base.
• Linear growth takes place which allows the lengthening of bones.

Question 2. Write short answer on growth pattern and their importance in orthodontics.
Answer. Pattern is defied as defiite arrangements of design in definite proportional relationship. In the growth pattrn is defined as proportional relationship over the time.

The pattrns are controlling of the restricting mechanisms to preserve integration of parts of our body under varying conditions or through the time.

Endochondral Ossification Process

Various contributors to the growth pattrn are cephalocaudal growth, scammon’s growth and predictability.

Predictability: This denotes the predictable sequences of changes in growth proportions of an individual.