Limits of the musculoskeletal system 2 - Lecture 4 Flashcards
What is the role of articular cartilage?
- Transfers forces between articulating bones
- Distributes forces in joints
- Allows relative movement between articular surfaces with minimal friction
What are some characteristics of collagen?
- provides tensile stiffness and strength
- Tensile strength of 100MPa (similar to nylon)
- Little resistance of shear
What are some characteristics of proteoglycans?
- Give cartilage disco-elastic properties
- Highly negative electro-static charge
- Attracted to water
What are some physical properties of cartilage?
Tensile properties (determined by arrangement of collagen - parallel better than perpendicular)
Compressive properties (determined by proteoglycan content - stiffness lower at surface and greatest in middle zones)
Shear properties
Visco-elasticity (associated with movement of water in the tissue)
What happens in the failure of cartilage?
Remodelling response when damaged is limited as chondrocytes synthesise new matrix but it never returns to normal strength even if damage is minor
Why does cartilage fail?
Acute injury (heavy lifting) Chronic Injury (interfacial wear form lack of lubrication, fatigue wear from cyclic stress)
What are the menisci?
Fibrocartilage (spacers and stabilisers and shock absorbers)
What happens in a magnetic resonance imaging machine? (MRI)
Strong magnetic field aligns the protons.
Perpendicular magnetic field pulses at different frequencies to disturb protons form alignment.
Different tissues of the body re-align at different speeds emitting different radio-frequencies
Why choose an MRI?
3D image Great contrast of different soft tissues Lengthy (40-60 mins) Expensive (£350) No ionising radiation
Why could an MRI kill a patient?
Loose metal e.g in eye of brain Pacemakers Spinal stimulators Cochlear implants Some valves and stents Chlostrophobia
What is an arthroscopy?
Surgical technique to view inside the joints
What is an osteoarthritic knee?
Degenerative condition of cartilage and underlying bone
Most common in hip, knee and lower back
Occurs in -15% of population over 60
Caused by mechanical stress with insufficient repair
What is a ligament?
Bone to bone
Stabilise joint
Restrict movement
What is a tendon?
Muscle to bone
Store and retain elastic energy
create moevement
What are ligaments and tendons made up of?
Cells - Fibroblasts Water Collagen Proteoglycans Elastin
Mechanical limits of the ligament/tendon?
The more collagen fibres to greater the resistance to stretch
What are some common ligament injuries?
ACL
MCL
Calceaneal fibrular ligament
Anterior Talo fibular ligament
How does a ligament heal?
Influx of blood cells to damaged area cause inflammation and pain New collagen fibrils laid down Scar tissue forms Scar tissue remodels Can take years
What architectural parameters make muscles different?
Size Fibre length Pennation length Fibre type Tendon length
