Bone and cartilage Flashcards
The cortical, compact bone is the dense outer plate. What percentage of the skeleton is made up of this bone?
- 80-85% of skeleton
The cancellous, spongy bone is the internal trabecular scaffolding. What percentage of the skeleton is made from this?
- 15-20%
In alveolar bone, what does the cortical bone have?
- Nutrient canals, containing blood vessels
What is the cortical bone lining the tooth sockets penetrated by and what is the bone also called?
- Bundles of collagen fibres of PDL (Sharpey’s fibres)
- Also called ‘bundle’ bone
What is the composition of bone (by weight)
- 60% inorganic
- 15% water
- 25% organic
Bone is composed of 60% inorganic material. What is this ?
- Hydroxyapatite
Bone is composed of 25% organic material. What makes up this? (3 points)
- Collagen (90%)
- Glycoproteins
- Proteoglycans
What 4 different glycoproteins make up the 25% organic part of bone composition?
- Osteocalcin
- Osteonectin
- Osteopontin
- Sialoproteins
The ECM of bone is composed of ‘ground substance’ what is this?
- A semi-fluid gel
- Has long polysaccharide molecules
The ground substance of the ECM of bone contains Glycos-amino-glycans (GAG’s). What are 4 main ones and what are they recognised as targets of?
- Chondroitin sulphate
- Dermatan sulphate
- Heparan sulphate
- Keratan sulphate
- Some of these are recognised as targets of pathgens that resorb bone
The ECM of bone contains fibres that reinforce the extracellular ground substance. What are 3 examples of these?
- Collagen
- Elastin
- Other non-collagenous proteins
What are the 2 types of bone on a microscopic level?
- Woven bone
- Lamellar bone
Is woven bone laid down rapidly or slowly?
- Rapidly
Is lamellar bone laid down slowly or rapidly?
- Laid down more slowly
What is the deposition of collagen like in woven bone?
- Irregular deposition of collagen
What is the deposition of collagen like in lamellar bone?
- Collagen fibres laid down in parallel
Which type of bone is present in fetus?
- Woven bone
The presence of which type of bone suggests the presence of a fracture?
- Woven bone
- For fracture repair (callus)
Which type of cells are found in a high number in woven bone?
- Osteocytes
Which type of bone is the normal form of bone in adults?
- Lamellar bone
Which type of cells are there few of in lamellar bone?
- Osteocytes
What is the structure of compact bone? (5 points)
- Laid down in concentric lamellae (lamellar bone)
- Form longitudinal columns
- Organised in HAversian systems around central (Haversian) canal
- Lateral (Volkman’s) canals
- Canals contain blood vessels
In compact bone, the bone is laid down in concentric lamellae. What is another name for this bone?
- Lamellar bone
What kind of columns are formed in compact bone?
- Longitudonal columns
What is the name of the central canals found in compact bo ne?
- Haversian canals
What is the name of the lateral canals found in compact bone?
- Volkman’s canals
What do the canals in compact bone contain?
- Blood vessels
Cancellous bone is a network of thin trabeculae with loads of space. What do the trabeculae consist of?
- Lamellae
Are osteocytes present in cancellous bone?
- Yes
Is the Haversian system present in cancellous bone?
- No obviuos Haversian system
In cancellous bone, the bone is thin. What does this allow to diffuse in?
- Nutrients
What is present in the spaces between trabeculae in cancellous bone?
- Bone marrow
Where do osteoblasts lie?
- On the surface of bone
Which kind of stem cells are osteoblasts derived from?
- Mesenchymal stem cells
Osteoblasts will synthesise and secrete collagen fibres forming a matrix that will mineralise into bone. What is the matrix mineralised by?
- Calcium salts
What are osteocytes?
- Osteoblasts that become trapped in mineralised bone
Where do osteocytes lie in bone?
- Lie within spaces - lacunae
How do osteocytes contact other osteocytes?
- Via cytoplasmic processes that run in canaliculi
What other cells do osteocytes appear to communicate with?
- Osteoblasts
Canaliculi radiate in one direction. What direction is this?
- Radiate towards nutrients that are coming from the PDL
Osteoclasts are large, multinucleated cells. Where are they derived from?
- Derived from haemaopoietic stem cells
Which type of defence cell are osteoclasts related to?
- Macrophages
What is the function of osteoclasts?
- They resorb bone (acid phosphatases)
Where do osteoclasts lie?
- In concavities in bone: Howship’s lacunae
Where is our main storage of calcium?
- In our bones
- 2.4 millimolar concentration of calcium is maintained and stored in our bones
What is bone remodelling?
- The removal and replacement of bone tissue, without change in the overall shape
In bone remodelling what is resorption balanced by?
- Balanced by deposition (apposition)
Each year, how much of the cortical bone and cancellous bone is replaced by the process of bone remodelling?
- Cortical bone = around 2%
- Cancellous bone = a round 25%
Which cells is the process of bone remodelling controlled by?
- Controlled by osteoblasts
What is the process of bone remodelling regulated by? (2 points)
- Hormones (PTH and calcitonin)
- Paracrine’s (various cytokines)
What is the reversal line In bone remodelling?
- Scalloped edge that shows where bone resorption changes to bone deposition
Tooth movements require remodelling of adjacent soft and hard tissues. When do these movements occur? (3 points)
- During eruption
- Post-eruptive (e.g. mesial drift)
- Orthodontic forces
What is cartilage?
- A semi-rigid, unmineralised connective tissue
The matric of cartilage is similar to bone. What is it composed of? (2 points)
- Ground substance
- Fibres
Where is hyaline cartilage found? (6 points)
- Widespread
- Larynx, nasal septum, trachea, ends of ribs (costal cartilages), articular surfaces, embryonic skeleton (precursor to bone)
Where can fibrocartilage be found? (2 points)
- Intervertebral disks
- Pubic symphysis
Where can elastic cartilage be found? (3 points)
- External ear
- Epiglottis
- Eustacian tube
What type of cells forms cartilage?
- Chondroblasts
When chondroblasts are trapped in the matrix what do they become?
- Chondrocytes
Is cartilage vascular?
- No, it has no blood vessels so if you cut into a tissue and there is no bleeding then it is probably cartilage
What has to diffuse into cartilage as there are no blood vessels?
- Nutrients
What can be present in thick areas of cartilage?
- Some channels
What do chondrocytes contain as a storage of energy?
- Stores of lipid and glycogen
What does ossification mean?
- Formation of or conversion into bone or a bony substance
What is endochondral ossification?
- Ossification that occurs in and replaces cartilage
What is intramembranous ossification?
- Ossification of bone that occurs in and replaces connective tissue
In what type of bone does endochondral ossification occur?
- ‘long’ bones
What is the process of endochondral ossification? (3 points)
- Cartilage precursor
- Cartilage proliferation
- Cartilage replaced with bone
In which type of bone does intramembranous ossification occur?
- ‘flat’ bones
- No cartilage precursor
Where in the bone does cartilage proliferation and growth occur?
- At the epiphysis
During endochondral ossification what happens at the hypertrophic zone?
- Cells become enlarged
During endochondral ossification what happens at the proliferative zone?
- Mitosis of cells here
What is the Spheno-occipital synchondriosis?
- The cartilaginous junction between the basisphenoid and basiooccipital bones of the mammalian skull that in humans is usually closed by the age of 25
What is achondroplasia?
- A genetic defect of cartilage growth
- Endochondral bone growth is impaired
- Intramembranous bone growth is unaffected
Which processes in the mandible have an important role in terms of bone remodelling in out lives and what are they important for? (3 points)
- Angular process
- Coronoid process
- Important for the insertion of muscles
What does an edentulous jaw lead to?
- The resorption of the alveolar process
