Bones Flashcards
What does morphological mean?
Relating to the form or structure of things
What does anisotropic mean?
Having a physical property which has a different value when measured in different directions
What two types of bone structure are found in long bones?
Cortical (compact) bone
Cancellous/trabecular (spongy) bone
What are the two phases or bone remodelling?
Resorption (break down of old bone)
Ossification (formation of new bone)
What are the 3 types of cell related to bone creation and remodelling?
Osteoblasts
Osteoclasts
Osteocytes
Osteoblasts:
- what is their function?
- where are they found (in relation to the bone)?
Ossification (formation) of new bone)
Found near the surface of bones
How do osteoblasts create new bone?
They:
- make osteoid (mainly collagen)
- secrete alkaline phosphatase (creates sites for calcium and phosphate deposition)
- allows crystals of bone mineral to grow
- osteoid becomes mineralised and forms bone
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What is osteoid?
Osteoid is an unmineralized organic tissue (mainly comprised of collagen) that eventually undergoes calcification and is deposited as lamellae or layers in the bone matrix
Where are osteoclasts found?
How do they break down bone?
On the surface of bones
They secrete acid phosphatase which un-fixes calcium in mineralised bone, breaking it down.
What are osteocytes?
Where are they found?
What is their function?
Osteoblasts which are no longer on the bone surface
Found in lacunae between lamellae
Maintain oxygen and mineral levels in bone
What are lacunae in bones?
Gaps within the lamellae (rings) of bone tissue in which osteocytes are to be found
What are the 2 mechanisms for creating bone in foetal development and what type of bone do they create?
- Endochronal ossification (long bones)
- Intramembraneous ossification (flat bones)
What are the stages of endochronal ossification?
- Development of cartilage model (rough shape of bone being formed)
- Osteoid calcifies, blood vessels grow into cavities within matrix
- Osteoblasts use calcified matrix as support structure to lay down more osteoid and form trabecullae
- Osteoclasts break down spongy bone to create medullary cavity
How does bone strength over time (from initial formation)?
Initially bone material deposited with collagen fibres in random directions (called woven bone)
Overtime, converted into lamellar bone (stronger due to aligned fibres)
Osteoid initially calcifies to produce cancellous bone
Where cortical bone required, more deposition of osteoid increeases bone density
What is woven bone?
What is the reason for its name?
Bone material initially deposited with collagen fibres in random directions
Collagen fibres woven together randomly
Where do secondary ossification centres appear in long bones?
At either end of bone
What is found between the primary and secondary ossification centres in long bones?
What is this made of?
What happens to this as the bone grows?
What eventually happens to this as bone growth ceases?
Epiphyseal plate
Cartilage
Continues to form new cartilage and replaced by bone (the bone increases in length)
Mid 20’s : the plate is replaced by bone and no further growth
What are the reasons for remodelling of bone?
- Reshape skeleton during growth
- Maintain calcium levels in body
- Repair microfractures caused by stress