Microstructure Of Bone Flashcards
What type of collagen is bone extracellular matrix
Type I - 90% of total protein highly organised fibres
What forms the osteoid in bone
Non collagenous proteins (glycoproteins and proteoglycans) and bone extracellular matrix
What are the 5 functions of bone
Protection
Support
Movement
Reservoir
Blood cell formation
What is cortical bone
The mature form of bone which the bundles of collagen fibres in bone matrix are organised into successive sheets or lamellae
What does the cortical bone form
The internal and external parts of flat bones and the external surfaces of long bones
What is the primary structural unit of cortical bone
An osteon also known as a Haversian system
What do insides of the bone contain
Trabecular bone like a honey comb
What is in between the spaces of bone and what do they make
Fluid bone marrow cells which make blood and some fat cells
What makes up 80% of the skeletal mass
Cortical bone
What makes up 20% of the skeletal mass
Cancellous/trabecular bone (spongy bone)
What is the difference between cortical and cancellous/trabecular bone
Cancellous/trabecular is less dense, more elastic and has a higher turnover rate
Where is cancellous/trabecular bone mainly found
Axial skeleton: bones of skull, ribs and spine
What is immature bone also known as
Woven bone
Where is woven bone found
During embryonic development
During fracture healing
In some pathological states
What is woven bone composed of
Randomly arranged collagen bundles and irregularly shaped vascular spaces lined with osteoblasts
What replaces woven bone
It is remodeled and replaced with cortical or cancellous bone expect in a few places
Where is woven bone not replaced
Places where tendons insert into bones and the tooth sockets
What are the 2 membranes which cover bone surfaces
Periosteum
Endosteum
What does the periosteum do
Around bone
Covers and protects the outer surface of the bones that are not covered by cartilage
What is the outer layer of the periosteum
A fibrous layer, a dense irregular connective tissue proper, is the protective layer
What is the inner layer of the periosteum
Is delicate, is osteogenic and contains mainly osteoblasts and osteoclasts
How is the periosteum connected to bone
With strands of collagen fibres (sharpeys fibres) that extend from its fibrous layer into the bone matrix
What is the outer periosteum connected to
Tendons, ligaments and the fibrous layer of the articular capsule in synovial joints
What is the endosteum
Inside bone
An osteogenic membrane
A delicate connective membrane containing mainly osteocytes and osteoclasts
What does the endosteum cover
All the bones inner cavities that contain marrow and or blood vessels
What are osteoblasts
Forms the collagen, glycoproteins and proteoglycans of the matrix and controls the deposition of mineral crystals on the fibrils
What are osteocytes
Mature osteocyte is involved in maintaining the matrix of its territory
Controls extracellular concentration of calcium and phosphorus
What are osteoclasts
Very large
Multi nucleated
Bone resorbing cells
What is the mineral content of alveolar bone
70%
What is the mineral content of cementum
70%
What happens at the 3rd week for bone development
Notochord develops (rod like structure that later becomes the spine, spinal cord and brain)
What happens on the 4th week of bone development
First signs of arms and legs
What happens on the 5th week of bone development
Coccyx forms and arms and legs take on definite shape
What happens on the 7th week of bone development
One inch long and facial features form
What happens on the 8th week of bone development
First bone cells appear
When does true ossification begin
After birth
