How is endochondral bone formed?
A cartilage model is made first which is replaced by bone
Describe how Haversian systems form
Osteoclast bore holes in bone in areas of stress
Vessels and endosteum colonise the holes
Layers of bone are laid down from the outside in
A narrow space between the vessels and bone is left - called the Haversian canal
What type of cartilage is present in intervertebral discs?
Where does most bone formation occur in relation to the growth plate?
On the shaft side edge of the plate
The addition of what to hyaline cartilage makes it elastic cartilage?
Which type of marrow is more haemopoetically active, yellow or red marrow?
Describe Haverian systems?
Long cylindrical columns of dense bone that run parallel to lines of stress
Where is most red marrow present in adults?
How is the diaphysis of new long bones first formed?
The cartilage is surrounded by bone that deny it nutrients therefore it degenerates and is replaced
Describe the cellular organisation of the growth plate
The proximal layer consists of normal cartilage (resting zone)
Then comes dividing chondrocytes (proliferation zone)
The mature chondrocytes (maturation zone)
Zone of hypertrophic, dying chondrocytes (hypertrophic zone)
Then degenerated chondrocytes are replaced by bone
What are osteocytes?
Osteoblasts that have been entombed in bone and are responsible maintenance of bone
What is the major type of collagen in hyaline cartilage ECM?
What is contained in the periosteum?
Is there periosteum in joints?
Where are osteoprogenitor cells located?
How does the composition of the nucleus propulsus change with age?
The gelatinous material - predominantly collagen type II is replaced by fibrocartilage after the age of 20
What do osteoprogenitor cells look like?
Describe the blood supply of bones?
Arteries end through the compact bone and branch inside the marrow to supply a larger area of bone from the inside
The periosteum has a separate blood supply
The epiphysis and diaphysis have a separate bone supply
What is tartrate-resistant acid phosphatase?
A blood marker of osteoclast activity that can be measured
What is synovial fluid derived from?
It's an ultrafiltrate of blood with added carbohydrates
Which structures contain elastic cartilage?
How do osteocytes communicate with vessels in the trabecular bone structure?
They send out processes that communicate directly with them
Why is the synovial membrane so leaky?
It lacks basement membrane, tight junctions and desmosomes
What are Sharpey's fibres?
Collagen fibres of tendons and ligaments that penetrate the bone surface and are continuous with collagen of the bone
Contrast the periosteum and endosteum?
Endosteum is thinner but contains more osteoprogenitor cells
What are the implications of the high nerve supply of bones?
Breaks are very painful
What structures have fibrocartilage?
Describe woven bone
New bone that forms during development and repair
More vascular and cellular
Lacks Haversian systems - is replaced by them
Are osteoclasts more related to osteoblasts or macrophages?
What is membrane bone?
Bone that developed directly from mesenchyme
eg the skull, bones of the face