Bone and Cartilage Flashcards
What are the two types of bone and how much of the skeleton do they make up?
- Cortical, compact bone
dense outer plate
80-85% of skeleton - Cancellous, spongy bone
internal trabecular scaffolding
15-20% of skeleton
What is the structure of cortical bone and what is it’s alternative name?
- Cortical bone has nutrient canals, containing blood vessels
- Cortical bone lining tooth sockets is penetrated by bundles of collagen fibres of PDL (Sharpey’s fibres)
- This bone is also called ‘bundle’ bone
What is the compositon of bone?
60% inorganic
25% organic
15% water
What is the organic component of bone made of?
- Collagen (90%)
- Glycoproteins
– Osteocalcin
– Osteonectin
– Osteopontin
– Sialoproteins - GAGS
– Hyaluronic acid - Proteoglycans (GAGs)
– Chondroitin SO4
– Dermatan SO4
– Keratan SO4
– Heparan SO4
What organic components are present for repair?
Glycoproteins
Osteocalcin
Osteonectin
Osteopontin
Sialoproteins
What does the ground substance of bone behave like?
semi-fluid gel
What fibres are found in ECM of bone?
– Collagen
– Elastin
– Other non-collagenous proteins
What are the characteristics of woven bone?
- rapidly laid down
- Irregular deposition of collagen
- present in fetus,
- fracture repair (callus)
- contains many osteocytes
What are the characteristics of lamellar bone?
- laid down more slowly
- Collagen fibres laid down in parallel
- normal form in adult
- contains fewer osteocytes
What is the structure of compact bone?
- Laid down in concentric lamellae (lamellar bone)
- Form longitudinal columns
- Organised in Haversian systems (oseteon) around central (Haversian) canal
osteocytes within lacunae communicating via canaliculi
- Lateral (Volkman’s) canals
- Canals contain blood vessels
What is the structure of cancellous bone?
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 characteristics of osteoblasts?
- Lie on surface of bone, inner layer of periosteum
- Derived from mesenchymal stem cells
- Synthesise and secrete collagen fibres forming a matrix
- The matrix is mineralised by calcium salts
What are characteristics of osteocytes?
- Osteoblasts that become trapped in mineralised bone
- Lie within spaces - lacunae
- Contact other osteocytes via cytoplasmic processes that run in canaliculi
- Osteocytes also appear to
communicate with osteoblasts (which are at the surface of the bone)
- Osteocytes also appear to
What are the characteristics of osteoclasts?
- Large, multinucleate cells, derived from haemopoietic stem cells
- Related to macrophages
- They resorb bone (produce acid phosphatases)
- Lie in concavities in bone : Howship’s lacunae
What is bone remodelling?
- Removal and replacement of bone tissue, without change in overall shape
- Resorption balanced by deposition (apposition).
What is bone remodelling controlled by and what is it regulated by?
The process is regulated by:
– hormones (e.g. parathyroid hormone, calcitonin)
– Paracrines (various cytokines)
Controlled by osteoblasts
What is the reversal line in histology?
Scalloped edge that shows where bone resorption changes to bone deposition.
What does tooth movement require?
require remodelling of adjacent soft and hard tissues
When do tooth movements occur?
- during eruption
- post-eruptive (e.g. mesial drift)
- orthodontic forces
What are the qualities of cartilage?
- Semi-rigid, unmineralised connective tissue
- Matrix is similar to bone:
–Ground substance
– Fibres
Where is hyaline cartilage found?
– Widespread
– Larynx, nasal septum, trachea, ends of ribs (costal cartilages), articular surfaces, embryonic skeleton (precursor to bone)
Where is fibrocartilage found?
– Intervertebral discs, pubic symphysis
Where is elastic cartilage found?
– External ear, epiglottis, Eustacian tube
What are qualities of cartilage cells and how are they formed?
Formed by chondroblasts
* These get trapped the matrix and become chondrocytes
* Avascular
* Nutrient diffuses in
* Some channels are present in thick areas of cartilage
What can chondrocytes store?
stores of lipid, glycogen which are nutrients as cartilage is avascular
What happens in endochondral ossification?
– Happens mostly in ‘long’ bones
– Cartilage precursor
– Cartilage proliferation
– Cartilage finally replaced with bone
What happens in intramembranous ossification?
– Happens mostly in ‘flat’ bones
– Bone formed from beginning in connective tissue
– No cartilage precursor
Where does cartilage proliferation and growth occur?
at the epiphyses of long bones
What is unique about the sphenoid-occipital synchondrosis? (base of skull)
it has a mixture of intramembranous and endochondral ossification
What bone is affected in achondroplasia?
genetic defect of cartilage growth.
Endochondral bone growth is impaired.
Intramembranous bone growth is unaffected.
What bone is developed in the TMJ?
endocondral
What processes in the mandible change shape throughout life?
condyle, coronoid, alveolar, and angular processes
What happens in edentulous jaws?
reduced processes especially alveolar process
What the remainder connective tissue surrounding the developing intramembranous bone will become?
Periosteum
Which cells are found surrounding the developing bone?
Osteoblasts
Which structures are found between the developing mandible and Meckel’s cartilage in this slide?
Inferior alveolar artery
Inferior alveolar nerve
What is the name of these cells trapped in bone?
Osteocytes
What tissues do you see lateral and posterior to the developing ramus of the mandible?
Masseter
Medial pterygoid
Parotid gland
What is the name of these multinucleated cells on the surface of bone?
Osteoclasts
What allows the skull to be passed through during birth?
The fontanelles are compressed as the head passes through the birth canal during child birth, this compression allows the skull to be squashed as it passes through.
What is amelogensis imperfecta caused by?
It is caused by the lack or of enzymes that are responsible for the breakdown of the organic matrix which would otherwise allow for the crystallites to finish their growth. Because of this the organic matrix is not fully broken down.
Nerve block vs infiltration?
block = injection will anesthetize multiple teeth in a quadrant. anesthetises branches
infiltration = Is when anesthetic is delivered to the terminal branches of the nerve and is confined to a small region of anesthesia
Where do you find the fovea palatinae?
anterior to hard palate
