Bone and cartilage Flashcards
What are the types of bone
Cortical, compact bone
-dense outer plate
-80-85% of skeleton
Cancellous, spongy bone
-internal trabecular scaffolding
-15-20% of skeleton
What penetrates the alveolar cortical bone lining tooth sockets
Bundles of collagen fibres of PDL
What is another name for the penetrated alveolar bone in tooth sockets
bundle bone
What is the composition of bone by weight
60% inorganic
-Hydroxyapatite
15% water
25% organic
Collagen (90%)
Glycoproteins
-Osteocalcin
-Osteonectin
-Osteopontin
-Sialoproteins
Proteoglycans (GAGs)
-Chondroitin SO4
-Heparan SO4
What are the types of microscopic bone
Lamellar bone
woven bone
What are the properties of woven bone
rapidly laid down
Irregular deposition of collagen
present in fetus,
fracture repair (callus)
contains many osteocytes
What causes the presence of woven bone
Fractures/breaks
What are the properties of lamellar bone
laid down more slowly
Collagen fibres laid down in parallel
normal form in adult
contains fewer osteocytes
Do canals contain blood vessels
yes
How is compact bone structured
Laid done in concentric lamellae (lamellar bone)
Form longitudinal columns
Organised in Haversian systems around central (Haversian) canal
Lateral (Volkman’s) canals
What are Volkman’s canals
Link haversian canals together
What are haversian systems called
osteons
Within osteons or haversian systems where were osteocytes present
Lacunae
How does cancellous bone appear histologically
Lots of space present
Network of thin trabeculae
Trabeculae consist of lamellae
Osteocytes present
No obvious Haversian systems
The bone is thin, and nutrients can diffuse in
Bone marrow present in the spaces between trabeculae
What are osteoblasts derived from
mesenchymal stem cells
What do osteoblasts do
Synthesise and secrete collagen fibres forming a matrix
How is the osteoblast matrix mineralised
Calcium salts
What forms the osteocytes in bone
They are the osteoblasts that become trapped in mineralised bone and lie within spaces (lacunae)
How do osteocytes communicate
Via cytoplasmic processes that run in canaliculi
What are osteoclasts derived from
Haemopoietic stem cells
How can osteoclasts be identified
Large multi-nucleated cells
Where are osteoclasts found
In concavities in the bone (Howships lacunae)
What is bone remodelling
The removal and replacement of bone tissue without change in overall shape
What percentage of cortical bone is replaced each year
2%
What percentage of cancellous bone is replaced each year
25%
What things regulate bone remodelling
Hormones (Parathyroid, calcitonin)
Paracrines (cytokines)
How can bone remodelling be identified in picture
Reversal lines:
Scalloped edge shows where bone resorption changes to bone deposition
When does tooth movement (remodelling ofsoft and hard tissues) occur
- during eruption
- post-eruptive (e.g. mesial drift)
- orthodontic forces
What is cartilage
Semi-rigid, unmineralised connective tissue
Matrix is similar to bone:
-Ground substance
-Fibres
What are the types of cartilage and where can they be found
Hyaline cartilage
-Widespread
-Larynx, nasal septum, trachea, ends of ribs (costal cartilages), articular surfaces, embryonic skeleton (precursor to bone)
Fibrocartilage
-Intervertebral discs, pubic symphysis
Elastic cartilage
-External ear, epiglottis, Eustacian tube
What is the most common cartilage
Hyaline cartilage
What produce cartilage cells
Chondroblasts
Are there blood vessels in cartilage
No (avascular)
Where are channels found in cartilage
Within thick areas
What are the types of bone growth
Endochondral ossification (‘Long’ bones)
-Cartilage precursor
-Cartilage proliferation
-Cartilage replaced with bone
Intramembranous ossification (‘Flat’ bones)
-Bone formed de novo in C.T.
-No cartilage precursor
What type of bone growth occurs in the skull
Intramembranous ossification
How does endrochondral ossification work
Initially, a cartilage skeleton is laid down.
The cartilage is replaced with bone.
There are several centres of ossification.
Where does cartilage proliferation occur
At the epiphyses
What stages does the cartilage go through to reach the final process of osification
Ossifying cartilage
Hypertrophic zone
Proliferative zone
Resting zone
What bone in the skeleten has a mixture of both types of bone growth
Base of the skull
Spheno-occipital synchondrosis
Cartilaginous joint that lies between the body of the sphenoid bone anteriorly and the basilar part of the occipital bone posteriorly
What is achondroplasia
A genetic defect of cartilage growth
Endochondral bone growth is impaired. Intramembranous bone growth is unaffected.
What type of bone growth develops the condyle
Endochondral bone growth
What parts of the mandible change shape during aging
Coronoid process (disappears)
Alveolar process (as teeth are lost it is resorbed)
Angular process (reduces)
