Musculoskeletal 3 Flashcards
Where are secondary osteons created?
Inside the existing bone tissue
What is the first step of secondary osteon formation?
Osteoclasts form and gather in an area that needs to be remodelled and this group of osteoclasts starts boring its way through the existing bone
What is the area where osteoclasts bore it’s way into existing bone called?
The cutting area- it creates a tunnel inside the existing bone
What’s the second step of secondary osteon formation?
After the tunnel has been created, osteoblasts move in and line the tunnel- they form the new active endosteum and start depositing osteoid onto the walls of the tunnel
Third step of secondary osteon formation?
Layer upon layer of new concentric lamellae are put down- a blood vessel will also grow into the tunnel to supply the active osteoblasts. The area is called the closing cone and moves along behind the cutting cone. Some of the osteoblasts are trapped in the newly deposited bone and become osteocytes
Fourth step of secondary osteon formation?
Eventually the tunnel is reduced to the size of a typical Haversian canal. The remaining osteoblasts living the Haversian canal either die it become bone lining cells (osteogenic cells) and contribute to the resting endosteum. A new osteon is formed. Sometimes a line can be seen at the junction between the outermost lamella of the new osteon and the pre-existing older bone. This is known as the cement line
What is the cement line?
A line seen at the junction between the outermost lamella of the new osteon and the pre-existing older bone
What’s the unit of spongy (cancellous) bone?
Trabecula
What’s the unit formation of spongy (cancellous) bone?
Grows outwards
Location of spongy bone?
Inside bones
Epiphysis of long bones
Unit of compact (cortical) bone?
Osteon (Haversian system)
Unit formation of compact (cortical) bone?
Grows inwards
Location of compact (cortical) bone?
The outer shell of bones
Diaphysis of long bones
Blood supply of compact (cortical) bone?
Blood vessels within Haversian and Volkmann’s canals
Blood supply of spongy (cancellous) bone?
Blood vessels in medullary cavity
Function of Spongy (cancellous) bone?
To support the outer cortex of compact bone in areas where forces occur from multiple directions. This is to help reduce the weight of bone. Rapid turnover of Ca and P
Function of compact (cortical) bone?
To provide a strong dense shell of bone on the outside, thickening in areas that are exposed to large forces
What is a joint or articulation?
Any point in which two (or more) bones interconnect
What’s the compromise of the Union of the joint/articulation?
A comprise between the need to provide support and the need to remain mobile
What can determine the function of a joint?
The different tissues and the shape of articulating surfaces
What does arthrosis mean?
Joint
Three functions of the joint?
- Movement
- Force transmission
- Growth
Definition of synarthrosis?
Immovable joint
Stability of synarthrosis?
High
Movement of synarthrosis?
Low
Location of synarthrosis?
Axial skeleton
Example of synarthrosis?
Sutures
Definition of amphiarthrosis?
Slightly movable
Stability of amphiarthrosis?
Moderate
Movement of amphiarthrosis?
Moderate
Common location of amphiarthrosis?
Intervertible discs in spine
Definition of diarthrosis?
Freely movable
Stability of diarthrosis?
Low
Movement of diarthrosis?
High
Location of diarthrosis?
Appendicular skeleton
Which joints are not restricted to the properties of a specific tissue or tissues which hold the ends of the bones tightly together?
Synovial joints
Apart from the articulate capsule, what are the ends of articulating bones in synovial joints like?
Mostly free
What does the, mostly free, ends of articulating bones in synovial joints allow for?
A wide range of motion, but can also introduce instability
What does the joint cavity contain?
Synovial fluid
What is articular cartilage?
A specialised type of hyaline cartilage (type of connective tissue)
What’s the primary function of articular cartilage?
To protect the ends of bones that come together to form a joint
Physical characteristics of articular cartilage?
Connective tissue forms a thin layer, typically 1-7mm thick, which is attached to the bone
What can articular cartilage do?
Absorb shock, support heavy loads and provide a smooth, near frictionless surface, when combined with synovial fluid
CoF of synovial fluid?
0.002-0.005
What needs to happen to articular cartilage in order for it to function for most of ones life?
The specialised tissue structure needs to remain intact
What is the degradation of the articular cartilage lead to?
Arthritis
What percentage of the articular cartilage are cells?
5%
What are the cells in articular cartilage?
Chondrocytes (chondro=cartilage)
What do chondrcytes do?
Build, repair and maintain cartilage
Where are chondrcytes located?
In spaces called lacunae
How do chondrcytes occur?
Depending on the zone, they occur by themselves or in groups called nests
What percentage of articular cartilage is the extra cellular cartilage?
95%
What percentage of the extra cellular matrix of articular cartilage is water and soluble ions?
75%
What is the water and soluble ion aspect of the EM?
The fluid phase that can move in and out of tissue
What percentage of the extracellular matrix of articular cartilage is fibre?
75% dry weight
What is the main fibre in the EM of articular fibre?
Collagen (mainly type 2)
What is the purpose of fibres in the EM of articular cartilage?
Provide the structural integrity to the tissue
What visitor structure of fibre like in the EM of articular cartilage like?
Has specific zonation patterns
What part of the articular cartilage is fibre?
The “solid phase” that’s fixed inside the tissue
What are the glycosaminoglycans in the extracellular matrix of the articular cartilage?
Hyaluronic acid, chondroitin sulphate, keratin sulphate
What is the main proteoglycan in the extracellular matrix of the articular cartilage?
Aggrecan
What is the purpose of the GAGs and PGs of the EM of the articular cartilage?
Provides the swelling and hydrating mechanism for the proper function of cartilage
What part of the articular cartilage is the GAGs and PGs of the EM?
Part of the solid phase that’s fixed inside the tissue
What zone in articular cartilage has low PG?
Surface zone
What part of the articular cartilage is calcified, and therefore has low PG?
Tide mark
What does the tide mark seperate?
Deep zone and calcified cartilage
What is the content of calcified cartilage like?
Low in PG, high in hydroxyapatite
What is the osteochondral junction also known as?
The cement line
Where in articular cartilage is lacunae found?
Calcified cartilage
What does the osteochondral junction seperate?
Calcified cartilage and subchondral bone
Does the cartilage contain blood vessels, nerves or lymphatics?
No, it’s avasvular and aneural
What zone has nests of chondrocytes?
Deep zone
Which zones does PG content increase?
From the middle zone to the deep zone
