Bone Biology- Block 3

What are the functions of bones?

Support and protection of soft tissue structures

Mineral reservoir and homeostasis

Hematopoiesis and lymphopoiesis

What is the epiphysis?

The cap on top of a bony structure

What is the metaphysis?

More spongey bone, between the epiphysis and diaphysis

What is the diaphysis?

In between physis

What is woven bone?

Immature bone

What is lamellar bone?

Mature bone

What are the types of lamellar bone?

Cortical or cancellous

What are the characteristics of cortical bone?

Thick at diaphysis and thin near bone ends

Compact or Osteonal bone

What are the characteristics of cancellous bone?

Trabecular or Spongy

What is an osteon also known as?

Haversion system

What is the purpose of a Volkmann’s or perforating canal?

Connection of Haversion systems

What type of material is the majority of bone made of?

Inorganic material (minerals)

What is the majority of bones’ organic component?

Type I Collagen

What regulates bone formation?

IGF, BMP, osteocalcin, osteonectin, bone sialoprotein, alkaline phosphate

What does collagen and EMC proteins provide?

Tensile strength to bone

What are components of ground substance?

Proteoglycans and glycosaminoglycans

What are the functions of osteoblasts?

Deposit osteoid

Initiate mineralization

Mediate osteoclast activity

What are the functions of osteocytes?

Communicate with neighboring cells

Regulate osteoblast and osteoclast actvity

Mechanosensors

What is the function of osteoclasts?

Bone resorption

What is the periosteum?

Membrane that surrounds bone

What is the component of the outer layer of the periosteum?

connective tissue

What is the inner layer of the periosteum?

Cambrium (blood vessels supply outer 1/3)

What does hydroxyapatite contribute to?

Strength in compression

What is intramembranous ossification? 

Osteocytes get entrapped and osteoblasts stay on top

What is an example of intramembranous ossification?

flat bones

What is endochondral ossification?

Hyaline cartilage template is resorbed and replaced with bone

What are examples of endochondral ossification?

Long bones, secondary fracture healing

During what zone do chondrocytes mature/enlarge?

Hypertrophic zone 

What occurs after apoptosis of chondrocytes?

Angiogenesis

When does apoptoses of chondrocytes occur?

Calcification

What happens during ossification?

osteoblasts form woven bone

What is bone modeling?

changes in bone size and shape during normal development

formation and resorption occur at different sites

What is bone remodeling?

Resorption then formation on same surface

What is a cutting cone?

Osteoclasts tunnel through bone followed by osteoblasts which lay down osteoid

What is the difference between cancellous and cortical remodeling? 

No need for blood vessels in cancellous remodeling

What drive remodeling?

Wolff’s law

What does decreased activation of remodeling and increased formation lead to?

Increased bone mass

What does increased activation of remodeling lead to?

Decreased bone mass

What is primary healing?

Contact or gap healing, no callus

What is secondary healing?

Heals with callous formation

What are the 5 phases of secondary healing?

1. Inflammation

2. Intramembranous ossification

3. Soft callus

4. Hard callus

5. Remodeling phase is long

Which type of healing results in stronger bone?

Secondary healing