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Bone Osteogenesis
Bone Development - Osteogenesis
2 forms of bone development:
1. Intramembranous Ossification
On or within a fibrous connective tissue membrane
Mesenchyme, Osteoblasts, Osteocytes
Formation of Flat bone
2. Endochondral Ossification
On cartilage from membrane
Chondrocytes replaced by osteoblasts
Formation of long bones
Intramembranous Ossification
Step 1
Mesenchymal cells cluster together
and differentiate into osteoblasts in
regions known as ossification
centres
Bone Osteogenesis 1
, Osteoblasts secrete osteoid (uncalcified bone matrix)
Calcium salts bind to minerals in the matrix, causing it to
harden
As this occurs, osteoblasts become trapped within the
mineral, becoming osteocytes
The bone expands as a series of spicules that spread into
surrounding tissues
Step 2:
As spicules interconnect, some
blood vessels become trapped
within the developing bone
Entire region of calcified spicules
become covered with compact
mesenchymal cells that become the
periosteum
Step 3:
Over time, the bone assumes the
structure of spongy bone
Areas of spongy bone may later be
removed, creating medullary
cavities
Through remodeling, spongy bone
formed in this way can be
converted to compact bone
Bone Osteogenesis 2
Bone Osteogenesis
Bone Development - Osteogenesis
2 forms of bone development:
1. Intramembranous Ossification
On or within a fibrous connective tissue membrane
Mesenchyme, Osteoblasts, Osteocytes
Formation of Flat bone
2. Endochondral Ossification
On cartilage from membrane
Chondrocytes replaced by osteoblasts
Formation of long bones
Intramembranous Ossification
Step 1
Mesenchymal cells cluster together
and differentiate into osteoblasts in
regions known as ossification
centres
Bone Osteogenesis 1
, Osteoblasts secrete osteoid (uncalcified bone matrix)
Calcium salts bind to minerals in the matrix, causing it to
harden
As this occurs, osteoblasts become trapped within the
mineral, becoming osteocytes
The bone expands as a series of spicules that spread into
surrounding tissues
Step 2:
As spicules interconnect, some
blood vessels become trapped
within the developing bone
Entire region of calcified spicules
become covered with compact
mesenchymal cells that become the
periosteum
Step 3:
Over time, the bone assumes the
structure of spongy bone
Areas of spongy bone may later be
removed, creating medullary
cavities
Through remodeling, spongy bone
formed in this way can be
converted to compact bone
Bone Osteogenesis 2
