Flashcards in Musculoskeletal 2 Deck (25):
Where are blood vessels in bone?
In the periosteum and in the medullary cavity
What does bone remodelling comprise of?
Appositional growth and bone resorption
What do perforating (sharpey's) fibre do?
Anchors structure to bone
What deposits osteoid?
Can tissue bone grow by interstitial growth?
No, it's too rigid
What is interstitial growth?
A process which involves cells dividing, secreting more extra cellular matrix and growing the tissue from within
Where does interstitial growth occur?
In softer tissue that can deform
Why does interstitial growth also not occur in bone?
Because bone is designed to resist deformity so it can only grow by adding new bone to an existing surface (appositional growth)
Where do appositional growth and bone resorption occur?
Through out the skeletal system, often completely independent of each other (aka bone remodelling)
How do long bones grow in length?
By endochondral ossification
How do osteoblasts deposit new bone onto a surface (appositional growth)?
In layers or sheets called lamellae
What is the collagen fibre arrangement like in lamellar (mature) bone?
Typically put down in the same direction within a layer, but can alternate up to 90 degrees out of phase between the layers
What does the arrangement of collagen fibres allow for?
Bond to withstand forces from different directions, making it significantly stronger
What are the two forms of lamellar bone?
Spongy and compact
Where does lamellae occur?
What is the normal thickness of compact bone?
Less than 0.4mm
Thickness of trabeculae?
Where are primary osteons formed?
Around a existing blood vessel on the surface of bone (normally in the periosteum)
When does primary osteon formation occur?
When the bone is growing and new bone tissue is being deposited into an existing surface
What is another name for compact bone?
What is another name for spongy bone?
Cancellous or trabecular bone
First step of osteon formation in compact bone?
Osteoblasts in the active periosteum either side of the blood vessel put down new bone forming ridges
Second step of osteon formation in compact bone?
As the bone continues to grow, ridges come together and fuse, forming a tunnel around the blood vessel. The tunnel is now lined with endosteum
Third step of osteon formation in compact bone?
Osteoblasts in the endosteum build concentric lamellae onto the walls of the tunnel. The tunnel is slowly filled inward toward the centre forming a new osteon