Osteogenesis By,M. Thiru murugan Growth and Ossification of bones: Ossification, or osteogenesis, is the process of bone formation. Parts of the skeleton form during the first few weeks after conception. By the end of the 8th week after conception, the skeletal pattern is formed in cartilage and membranes and ossification begins. Bone development continues throughout adulthood. Even after adult, bone development continues for repair of fractures and for remodeling to meet changing lifestyles. Osteoblasts, osteocytes & osteoclasts are the 3 cells types involved in the development, growth & remodeling of bones. Stages of bone growth: Initial Bone Formation: The formation of bone during the fetal stage of development occurs by 2 processes: Intramembranous ossification & endochondral ossification. Intramembranous ossification is the process of bone development from fibrous membranes. It is involved in the formation of the flat bones of the skull, the mandible, and the clavicles. The steps in Intramembranous ossification are: Development of ossification center Calcification Formation of trabeculae Development of periosteum 3. Endochondral ossification  It is the process of bone development from hyaline cartilage. All of the bones of the body (except for the flat bones) are formed through endochondral ossification Endochondral ossification begins with points in the cartilage called “primary ossification centers.” They mostly appear during fetal development, though a few short bones begin their primary ossification after birth. These cartilage points are responsible for the formation of the diaphyses of long bones, short bones, and certain parts of irregular bones. Secondary ossification occurs after birth and forms the epiphyses of long bones and the extremities of irregular and flat bones. The diaphysis and both epiphyses of a long bone are separated by a growing zone of cartilage (the epiphyseal plate). When the child reaches skeletal maturity (18 to 25 years of age), all cartilage is replaced by bone, fusing the diaphysis and both epiphyses together (epiphyseal closure). 4. Remodeling: Even after skeletal maturity has been attained, bone is constantly being resorbed and replaced with new bone in a process called bone remodeling, it occurs throughout a person’s life long beyond the initial development of bone. Bone remodeling is carried out through the work of osteoclasts, which are bone cells that resorb bone and dissolve its minerals. Osteoblasts and osteoclasts are referred to as a bone remodeling unit. The purpose of remodeling is to regulate calcium homeostasis & repair micro-damage from everyday stress, as well as to shape the skeleton during growth. Bone repair: Bone repair (or healing) is the process in which a bone repairs itself following a bone fracture Minerals involved in ossification include: calcium, vitamin D, potassium, phosphorus, magnesium, iron, sodium & chlorine

1. Osteogenesis

2. Growth and Ossification of bones:
• Ossification, or osteogenesis, is the process of bone formation.
• Parts of the skeleton form during the first few weeks
after conception.
• By the end of the 8th week after conception, the skeletal pattern is
formed in cartilage and membranes and ossification begins.
• Bone development continues throughout adulthood.
• Even after adult, bone development continues for repair of
fractures and for remodeling to meet changing lifestyles.
• Osteoblasts, osteocytes & osteoclasts are the
3 cells types involved in the development, growth & remodeling
of bones.

3. • Stages of bone growth:
1. Initial Bone Formation: The formation of bone
during the fetal stage of development occurs by
2 processes: Intramembranous ossification &
endochondral ossification.
2. Intramembranous ossification is the process of
bone development from fibrous membranes. It is
involved in the formation of the flat bones of the
skull, the mandible, and the clavicles.

4. The steps in Intramembranous ossification are:
• Development of ossification center
• Calcification
• Formation of trabeculae
• Development of periosteum
(At the ends of long bones is full of holes that
are connected to each other by thin rods and
plates of bone tissue known as trabeculae.)

5. 3. Endochondral ossification
• It is the process of bone development from hyaline
cartilage.
• All of the bones of the body (except for the flat bones)
are formed through endochondral ossification
• Endochondral ossification begins with points in the
cartilage called “primary ossification centers.”
• They mostly appear during fetal development, though a
few short bones begin their primary ossification after
birth.

6. • These cartilage points are responsible for the formation of the
diaphyses of long bones, short bones, and certain parts of
irregular bones.
• Secondary ossification occurs after birth and forms the
epiphyses of long bones and the extremities of irregular and flat
bones.
• The diaphysis and both epiphyses of a long bone are separated
by a growing zone of cartilage (the epiphyseal plate).
• When the child reaches skeletal maturity (18 to 25 years of
age), all cartilage is replaced by bone, fusing the diaphysis and
both epiphyses together (epiphyseal closure).

7. Endochondral ossification

8. 4. Remodeling:
• Even after skeletal maturity has been attained, bone is constantly being
resorbed and replaced with new bone in a process called bone remodeling, it
occurs throughout a person’s life long beyond the initial development of bone.
• Bone remodeling is carried out through the work of osteoclasts, which are
bone cells that resorb bone and dissolve its minerals.
• Osteoblasts and osteoclasts are referred to as a bone remodeling unit.
• The purpose of remodeling is to regulate calcium homeostasis & repair
micro-damage from everyday stress, as well as to shape the skeleton during
growth.
• Bone repair:
• Bone repair (or healing) is the process in which a bone repairs itself
following a bone fracture
• Minerals involved in ossification include: calcium, vitamin D, potassium,
phosphorus, magnesium, iron, sodium & chlorine