Bone Flashcards
What are some of the functions of bone?
Weight bearing/support
Protection
Mineral store
Blood formation
What is the gross anatomy of a bone composed of?
Compact bone
Spongy bone
Blood vessels
Medullary cavity
Bone marrow
Membranes (periosteum/endosteum)
What are the circular structures that compact bone is organised into?
Osteons/Haversian systems
What are the osteons/Haversian canals composed of?
Central Haversian canal and horizontal perforating/Volkmann’s canals where blood vessels are
What is found in Volkmann’s canals?
Blood vessels
What is found in the Haversian canal?
Osteocytes and concentric rings of bone marrow
What is an osterocyte?
A bone cell
What is more dense out of spongy and compact bone?
Spongy bone
What network is found in spongy bone?
Network of lamellated trabeculae filled with bone marrow
What is the lamellated trabeculae filled with?
Bone marrow
Are Haversian systems found in spongy bone?
No
What does the orientation of trabeculae reflect?
Direction of the mechnical force
What are some different types of bones?
Flat bone (frontal)
Sutural bone
Short bone (carpal)
Irregular bone (vertebra)
Sesamoid bone (patella)
Long bone (femur)
What are the 2 types of bone formation?
Endochrondral
Intramembraneous
What is the process of endochondrial ossification?
- Bone forms as cartilage model
- Blood vessels invase cartilage
- Cartilage replaced with bone
- Cartilage reamins in epiphyseal growth plate, which eventually ossifies
What is ossification?
Process of laying down new bone material by cells called osteoblasts
What is the process of intramembraneous ossification?
- Mesenchymal cells develop into osteoprogenitor cells that mature into osteoblasts that start developing bone
- Residual mesenchymal cells develop blood vessels and bone marrow
What are the 3 cells that make up bone?
Osteoblasts
Osteocyte
Osteoclasts
What do osteoblasts do?
Form new bone
What do osteoclasts do?
Destroys old bone
What is the extracellular matrix composed of?
45% hydroxyapatite crystals (complex form of calcium phosphate)
35% collagen (type I)
20% water
What do minerals do to bones?
Make them stiff and give them strength
What does collagen do to bones?
Gives them flexibility, increasing strength under tension
Why is bone dynamic?
Due to bone turnover, new bone is constantly being formed
What is the process of new bone constantly being formed?
- Osteoclasts break down old bone
- Osteoblasts build new bone
Are osteoblasts immature or mature?
Immature
What are osteoblasts derived from?
Osteopreginitor cells
What is a function of osteoblasts?
Produce the bone matrix
What do osteoblasts do when they are surrounding by matrix?
Become osteocytes
Are osteocytes mature or immature?
Mature
Where are osteocytes found?
Inside lacunae
What are osteocytes connected to each other by?
Canaliculi
What does canalucili allow?
Osteocytes to communicate with each other
What are functions of osteocytes?
Maintain the bone matrix
Sense mechanical force
What are osteoclasts derived from?
Haematopoietic stem cells
Where are osteoclasts found?
On bone surfaces
What is the function of osteoclasts?
Resorb bone matrix
What is the resorption pit of an osteroclast called?
Howship’s lacunae
When does bone disease occur?
When remodelling is not balanced
What are some examples of bone diseases?
Osteoporosis (resorption > formation)
Paget’s disease (resorption and formation greater)
Osteopetrosis (low resorption)
What is bone mass controlled by?
Genes and the environment
What happens to bone mass as you get older?
It decreases
How does mechnical load regulate bone mass?
You loss what you don’t use
