MSK: Week 3 Flashcards
What variables affect muscle contraction
- Length
- tension
Define Isometric Contraction
Contraction where tension changes but muscle length stays the same
Define isotonic contraction
Contraction where muscle length changes but tension stays the same
Define concentric contraction
Where muscle length shortens
Define Eccentric contraction
Where muscle length increases
Is the axon terminal of motor neurons myelinated
Yes
Where are acetylcholinesterase located
On the post-synaptic membrane junctions in the motor end plate
What are three biological roles of myosin
- Assembles into fragments
- Uses ATPase enzymes
- Binds to actin
Describe the structure of myosin
Has two heavy chains
Has four light chains
How large are the heavy chains on myosin
200,000 MW
What are the sizes of the light chains
1 pair = 16,000 MW
1 pair = 20,000 MW
Describe the structure of actin
F-actin filament consisting of G-actin monomers
F-actin filaments make a chain of two alpha helices
What is the size of a single G-actin monomer
41,800 MW
What structure is wrapped around the F-actin alpha helices
Tropomyosin
What is the role of Titin
Connects the Z-line to the M-line in the sarcomere
M-line = Middle of the sarcomere
It prevents over-stretching by recoiling
What is the molecular size of tropomyosin
35,000 MW
How often does a troponin complex appear along the tropomyosin chain
Every 38.5nm along
What does a troponin complex consist of
- TnI - Inhibitory
- TnT - Binds to tropomyosin
- TnC - Binds to calcium
Define fracture
Breach in continuity of bone
Name two ways fracture occur
Non-physiological loads applied to normal bone
Physiological load applied to abnormal bone
How do I describe on what part of the bone the fracture is located
Proximal 1/3
Middle 1/3
Distal 1/3
Define the following fracture names: Transverse Oblique Spiral Communicate Segmental Avulsed Impacted Torus Greenstick
- A transverse cut through the bone
- A diagonal cut through the bone
- A curved cut through the bone
- A crack on the bone
- Cuts through the bone that breaks it into segments
- A piece of bone that breaks off the tips of the bone
- A cut through the tip of the bone
- A swelling in the bone
- A semi-cut through the bone (not all the way through)
Define fracture angulation
Where the normal axis of the bone has been altered such that the distal bone points in another direction
Define an intra-articular fracture
A bone fracture in which the break crosses into the joint surface
This damages the cartilage always
What is the opposite of intra-articular fracture
Extra-articular
What two fracture patterns are unique to children
- Heals faster
- Bones are more plastic
Outline the stages of fracture healing
- Haematoma
- Inflammation
- Repair
- Remodelling
What happens during a haematoma
- Bleeding
- Blood clots at fracture site
- Periosteum stops
- Osteocyte death
What happens during an inflammation
- Fibrin clot organisation (platelets rich in chemoattractants)
- Neovascularisation (natural formation of new blood vessels)
- Cellular Invasion
What do haemotopoietic cells do during inflammation
They clear debris + produce repair cytokines
What do osteoclasts do during inflammation
Resorb dead bone
What happens during the process of repair
Callus formation:
Fibroblasts produce collagen
Chrondroblasts from cartilage
Osteoblasts produce asteroids
Matrix mineralisation occurs
Increased Vasculosity
Define the process of remodelling
- Woven bone structure replaced by lamellar bone
- Increased bone strength
- Healing
What are the three principals of fracture management
- Reduce (the fracture)
- Immobilise
- Rehabilitate (the patient)
What is the role of seasmoid bones
Reduce pressure and friction
Where are osteocytes and osteoblasts derived from
Mesenchymal cells (osteoprogenitor cells)
What do osteoblasts and osteocytes secrete
Osteoids
Where are osteoprogenitor cells loacted
Close to the bone surface
What happens to osteocytes during bone formation
Become trapped in the matrix they secrete
How are osteoblasts connected
Via canaliculi
What do canaliculi accomplish
Allow passive movement of O2 and nutrients
What is the role of osteocalcin
They have a high affinity for calcium
Difference in osteoid layout in woven and lamellar bone
In woven, it is disorganised
In lamellar, the osteoids are arranged in parrallel fibres
When do osteoids begin to mineralise
When the conc. of phosphates and calcium is high
What two enzymes allow mineralisation to take place
Osteocalcin
Alkaline Phosphatase
How does osteocalcin aid in mineralisation
Joins calcium together
What is bone arranged as in lamellar
Osteons
What is found in the centre of each osteon of lamellar bone
Central Haversian canal (containing blood vessels)
Where does intramembranous ossification take place
Flat bones of the skull
Cortical bone shafts
Where does endochondrial ossification take place
All other bone
When does intramembranous and endochondrial ossification take place
Both in the second trimester
Describe the process of intramembranous ossification
- Small clusters of progenitor cells within a primitive mesenchyme transform into osteoblasts
- These deposit isolated bone islands
- Islands enlarge + unite
- Deposition of bone continues until all the bones are filled in
P
What type of bone is produced during intramembranous ossifictaion
Woven bone
What type of synovial cells are found in the synovial joint
Type A - Phagocytic
Type B - RER rich
