Ossification is the term use to describe a process of bone fermentation by deposition of calcium in the fetal hyaline cartilage.

1. OSSIFICATION
Prof. Redem C. Deligero, MATMRS; MSES

2. OSSIFICATION

Ossification is the term use to describe a
process of bone formation by deposition of
calcium in the fetal hyaline cartilage.

All bones develope from the mesenchymal
tissue of the embryo

3. TYPES OF CALCIUM DEPOSITION
A. HUMORAL FACTOR

Relates in the concentration of
minerals in the body fluids and the
solubility of calcium salts and
phosphates.
B. LOCAL FACTORS

No further explanation but relates on
something about the determinants
when and where bone minerals will be
deposited.

4. CENTERS OF OSSIFICATION
1. PRIMARY CENTER OF OSSIFICATION

Ossification starts at the central part of the
cartilagenous model.

Portion of bone develop from this primary center
of ossification is called the diaphysis.

This normally appears before birth.
2. SECONDARY CENTER OF OSSIFICATION

This appears at the two ends of the long bones.

Usually appear after birth.

The portion of this bone developed is called
epiphysis.

5. LAWS OF OSSIFICATION
1. Epiphysis that ossify first fuse diaphysis
last. The epiphysis that ossify last fuses first
except the lower end of fibula.
2. Growing end of the bone is found at the
area of the epiphysis that appears first fuses
last.
3. The direction of the nutrients artery is
always away from teh growing end.
4. In long bones, growing ends fuse with the
shaft at about 20 years.

6. 2 TYPES OF OSSIFICATION
1. INTRAMEMBRANOUS

Bones that are develop directly from
embryonic mesenchymal tissue.

Usually occurs in the deep layers of the
dermis

E.g. Cranila Vault, Mandible, and Clavicle.
2. CARTILAGENOUS OSSIFICATION

Cartilage is formed first from the
mesenchymal tissue which later on ossify
to form the bone.

7. INTRAMEMBRANOUS OSSIFICATION
1. Formation of Matrix and Organic Components.

Osteoblast cluster and secrete organic matrix
components including collagen fibers.

Mineralization of matrix through crystallization of
calcium salts.

Differentiation of osteoblats into osteocytes.
2. Ossification Center Development.

Bone grow outward from this center called spicules.

Osteoblast formation continue from mesenchymal
cells.
3. Spongy Bone Formation

Subsequent remodelling around trapped blood
vessels resulted to compact bone.

8. INTRAMEMBRANOUS OSSIFICATION

9. CARTILAGENOUS OSSIFICATION
1. Cartilage Enlargement

Chondrocyte enlargement near the center of the shaft.

Surrounding matrix starts to calcify.

Death of chondrocytes due to nutrient deprevation.
2. Periosteum Formation

Perichondrium is converted to periosteum.

Perichondrium cells converted to osteoblast.

Inner organic layer produces thin layer of bone arround the shaft of
cartilage.
3. Spongy Bone Formation
 Osteoblast replaces calcified cartilagenous matrix.

Increase blood supply to perichondrium.

Capillaries and osteoblast invade spaces left by disintegrating
chondrocytes.
4. Marrow Cavity Formation

Bone is still spongy when its diameter is small.

As it enlarges osteoblast forms the marrow cavity.

10. OSSIFICATION PLATES
1. Zone of Reserve Cartilage - Chondrocytes randomly distributed
throughout the matrix and are mitotically active.
2. Zone of Proliferation - The chondrocytes rapidly proliferate that
form rows of isogenous cells that are parallel to the direction of
bone growth.
3. Zone of Maturation and Hypertrophy - Chondrocytes mature,
hypertrophied and accumulate gylcogen in their cytoplasm. The
matrix in their lacunae narrows with a corresponding growth of
lacunae.
4. Zone of Calcification - Lacunae becomes confluent, hypertrophied
chondrocytes die and cartilage matrix becomes calcified.
5. Zone of Ossification - Osteoprogenitor cells invade the area and
differentiate into osteoblast, which elaborate matrix that becomes
calcified on the surface of calcified cartilage. This is followed by
resorption of the calcified cartilage/ calcified bone complex.

11. OSSIFICATION PLATES