Bone Flashcards
What are the three main functions of bone?
- Weight bearing/support
- Mineral store
- Hematopoiesis
What is the name of the hard bone on the outside?
Cortical bone
How is cortical bone organised?
- Osteons
- Haversian systems
What are the two canals that exist in haversian systems?
- Central Haversian canal
- Horizontal volkmanns canal
What surrounds a haversian canal?
- Osteocytes
- Concentric rings of bone matrix
What is spongy bone called
Trabecular
What is the structure of trabecular bone?
- Network of lamellated trabeculae
Which direction do the trabeculae run?
In the same direction as the main mechanical force of the bone
What is the name of the cavity inside the bone
Medullary cavity
What are the 6 types of bone? (FISSSL)
- Flat
- Irregular
- Sesamoid
- Sutural
- Short
- Long
What are the two types of ossification?
- Endochronal
- Intramembranous
Which bones grow using endochronal ossification?
- Long bones
What bones grow intramembranously?
- Flat bones
Name the bones in the body that ossify intramembranously
- Flat bones in the skull
- Mandible
- Maxilla
- Clavicles
Describe the stages of endochondral ossification
- Cartilage model forms initially
- Blood vessels invade cartilage model
- Cartilage replaced with bone
- Cartilage remains at epiphyseal growth plate for growth
Describe the stages of intramembranous ossification
- No cartilaginous stage
- Mesenchymal cells mature into osteoblasts and start depositing bone
- Other mesenchymal cells become blood vessels
What three cells are involved in bone
- Osteoblasts
- Osteoclasts
- Osteocytes
What % of the extracellular matrix is hydroxyapatite?
45%
What does hydroxyapatite do to bones?
Makes them stiff and able to support structures
What % of the extracellular matrix is collagen?
35%
What does collagen give the bone?
Flexibility
What cells mediate the bones ability to remodel?
- Osteoclasts degrade old bone
- Osteoblasts build up new bone
In what membranes are osteoblasts created?
- Periosteum
- Endosteum
What is the osteoid?
Unmineralised matrix
What bone disease can result of greater reabsorption by osteoclasts than laying down of new bone by osteoblasts?
Osteoporosis
What disease results in a decrease of bone reabsorption?
Osteopetrosis
Why does bone mass reduce after menopause?
- Oestrogen normall inhibits bone breakdown
- Less oestrogen produced
