Bone Development

Composition of Bone

Approximately 33%-Organic Collagen Glycosaminoglycans (GAGs) Contain Chondroitin sulfate Resilience and toughness

Composition of Bone

Approximately 66% Inorganic Calcium phosphate (hydroxyapatite),

calcium carbonate and magnesium phosphate

Hardness and rigidity Radiopaque-xray cannot penetrate Decalcify with acid—bone biopsies Alkaline phosphatase plays a role in

mineralization

Review the components

Osteocytes Osteiod Lacunae Canaliculi

Review

Osteoblasts Form new bone Periosteum and endosteum holds in

reserve Osteoclasts

Bone destroying

Terms

Ossification=true bone formation Calcium deposited in osteoid matrix

Calcification=calcium salts deposited in other tissue Generally pathologic!!

Types of new bone formation

Endochondral ossification=replacing fetal cartilage model with bone

Intramembranous ossification=fibrous tissue infiltrated by osteoid tissue Flat bones-i.e. skull

Intramembranous Ossification

Endochondral Ossification

Cartilage pattern Ossification process starts in the midshaft

Replacing cartilage with bone Osteoblast or osteoclasts?

Ossification centers-primary (diaphysis) and secondary (epiphysis)

Physis-proliferation of cartilage Bone growth!

Ossification Centers

Primary Ossification Center

Secondary Ossification Center

Endochondral Ossification

What controls bone length growth??

Growth hormone Stimulates release of insulinlike growth factors

( in liver and cells near growth plate) Stimulate chondrocyte-increase cartilage

production in epiphyseal cartilage Androgens (Testosterone> estrogen)

Ultimately, brings on epiphyseal closure Stimulate ossification center vs. cartilage

production

Mechanical Stress to bone

Static vs. Dynamic load Stretch Compression Bending Torsion (twisting) Shearing

Remodeling

Continuous turnover of bone in mature animals Atrophy Hypertrophy Reshapes to minimize

mechanical stress

Hormonal control of remodeling

Types of Fractures

Simple vs. Open Fracture

Types of Fractures

Greenstick fractures vs.

Complete fracture

Types of Fractures

Physeal fracture –young animals

Where are the fractures??

Types of Fractures Comminuted fractures

Fracture Repair

Apposition and Immobilization Process

Clot formation Granulation tissue Periosteal and endosteal osteoblasts Release osteoid to produce callus Callus becomes ossified Remodeling-osteoclasts remove excess

Callus formation

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