Musco-skeletal Flashcards
Usage of word ‘bone’
As the organ, or the tissue
Functions of bone
Protection Support Movement Calcium/phosphorus reserve Haemopoeisis (red) Fat storage (yellow) (or please stop making children have fatalities)
Axial bone
Ribs, vertebrae, skull
Appendicular bone
All movement bones, non-axial
Red bones are
Axial
Yellow bones are
Appendicular
Longitudinal sections of a long bone
Epiphysis Metaphysis Diaphysis Metaphysis Epiphysis
Outer layer of bone
Periosteum (fibrocellular)
Inner layer of bone
Endosteum (fibrocellular)
Bone marrow located
Diaphysis
Sharpey’s fibres
Fibres joining periosteum to endosteum
ECM of bone
Fibre -> Collagen (I,V) for stretch and pull
Ground substance -> hydroxyapatite for squeezing and compression
Cells of bone
Osteogenic stem cell Osteoblast Osteocyte Osteoclast For torsion forces (twisting)
Articular cartilage
Outside layer of epiphysis, where periosteum is not
Layers of epiphysis
Articular cartilage, compact bone, spongy bone
Medullary cavity
Spaces in-between bone, or trabeculae
Spongy bone design
Trabeculated, covered in endosteum, for support of perpendicular forces
Mesenchyme stem cells give rise to ____ what is this cells function/location?
Osteogenic cells, found in peri/endosteum and central canal of compact bone, lays dormant mainly, divides into other bone cells (not osteoclast)
Osteoblasts location function and precursor
Location - Where bone is forming, peri/endosteum
Function - To form new bone by making osteoid
Precursor - Osteogenic stem cells
Osteocytes function, location and precursor
Location - Lacunae, cell processes through canaliculi
Function - Maintenance of bone, communication to other osteocytes. Cellular processes extend to other osteocytes
Precursor - Osteoblast gets trapped in lacunae and becomes osteocyte
What is osteoid made of
Collagen
Precursor of osteoblast
Blood monocyte progenitor cell fusion
How are osteoblasts formed
Monocyte progenitor cells fuse to form a syncytium
Function/shape of osteoclast
Large, multinucleated cell, convoluted.
Secretes acid and acid activated enzymes to break down hydroxyapatite and proteins
What happens after osteoblasts break down bone?
Endocytosis/exocytosis
Space between bone tissue and osteoclast
Howship’s lacunae
A section of bone has only flat cells. What is this cell type, and what is the state of this section of tissue?
Osteogenic cells, resting
Difference in diameter of adults bone from childrens
Adult has wider diameter, but just larger lumen. Width of tissue wall similar
Why can’t bone grow through interstitial growth
Too dense
What is the growth of bone called?
Appositional growth
Outline bone growth
On periosteum, appositional growth occurs
At endosteum, reabsorption occurs.
Outline appositional growth
Signal to ostegenic cell
Cells multiply to create osteoblasts
Osteoblasts reside between osteogenic cells and bone tissue
Osteblasts lay osteiod, some become trapped and turn into ostecytes
Osteiod is calcified
Osteoblasts die, or revert to osteogenic cells
When do canaliculi grow
During bone formation
Ricket’s disease
Lack of calcification from malnutrition
Outline bone reabsorption
Monocyte progenitor cells combine to create a syncytium (osteoclast)
Osteoclast at endosteum, moves between bone tissue and osteogenic cells
Secrets acid and enzymes to break bone down
Broken down bone is endocytosed and then exocytosed
Osteoclasts undergo apoptosis
Why do bones have different strengths at different ages?
Ratios between rates of appositional growth and bone reabsorption change
How do long bones lengthen?
At epiphysis, articulate hyaline cartilage grows outward due to chondrocytes, boarder where articulate cartilage meets epiphysis is where cartilage dies and bone is replaced instead
Epiphyseal line
Where articulate plate origninally sat
Types of bone
Woven bone and lamellar bone
Outline properties and instances of woven bone
Found in infants and following tissue trauma.
Wavy collagen fibers
Not a dense arrangement
Cannot withhold tension
Is like this as bones were under no tension in the womb
Outline properties and instances of lamellar bone
In grown adults/mature bone Very strong Collagen layers multidirectional layering means tension can be withheld from multiple directions
Outline spongy bone properties/where it can be found
Found at epiphysis Trabeculated Trabeculae covered in endosteum Lots of osteoclasts Blood vessels are found in medullary cavity Grows from outwards inwards layered bone
How come osteocytes in trabeculae of spongy bone get nutrients?
Only can be a certain thickness
Outline compact bone properties/where it can be found
Found in diaphysis
Cylindrical layers called osteons
Volkmann’s canal/haverstian canal runs through oseons
Nutrients goes from inside to outside
Types of lamellar bone
Circumferential
Interstitial
Concentric
How are primary osteons formed
During appositional growth, periosteum grows faster than bone, which creates ridges that become enclosed
After this, The endosteum of the ring forms bone inwards to narrow the tunnel (blood vessels reside here)
What is the type of lamellae found in osteons?
Concentric
Issue with excess circumferential lamellae?
Increased distance, difficulty designing blood supply
How are secondary osteons formed
Monocyte progenitor cells from blood vessels leave blood vessel, forming syncytiums (osteoclasts)
Osteoclasts form a cutting cone, or drill that moves through the old bone clearing it away 1mm/20days
osteogenic cells move in behind, forming endosteum
Endosteum lays down new bone from outside inwards
blood vessels following the osteoclasts
What is the cement line
Where new bone has began to form against old bone
Maximum width of bone for blood/nutrient perfusion
0.4mm
In X-ray, how is new bone identified
Darker due to less calcification, probes leave larger inprint as bone is softer
Define an arthrosis
Any point where 2 or more bones meet
Functions of arthrosis
Movement
Force transmission
Growth
What is the fontanelle
Soft region of diarthrosis on babies head
Typer of arthrosis
Synarthrosis
Amphiarthrosis
Diarthrosis
Function of synarthrosis
high stability, low movement, in axial skeleton, absorb forces
Function of amphiarthrosis
Some movement, not entirely free movement, some stability
Function of diarthrosis
Freely mobile, low stability
Ankylosis
fusion of arthrosis
What tissue type are simple synovial joints
Diarthrosis joints
Features of synovial joints
Articular cartilage
Articular Capsule
Joint cavity
Synovial fluid
What is articular cartilage
Specialized hyaline cartilage
Function of articular cartilage
Protection of the ends of bones, support, shock absorption, friction-less surface, heavy loads etc
What is articular cartilage made of
Cells (5%)
- Chondrocytes
ECM (95%)
- Ground substance
- Water, soluble ions, GAGs and PGs
- Fibres
- Collagen type llFunction of glycosaminoglycans and proteoglycans in articular cartilage
Water compartment/swelling of tissue
Forces which cartilage resists
Expansion (swelling force), compression, shear
Regions/zones of articular cartilage
- Surface zone (5-10%)
- Low PG, horizontal fibers for shear force - Middle zone (40-45%)
- More collagen & PG
- Les compact arrangement
- Criss-cross or 45 degree fibers - Deep zone
- Nests of cells
- Most PG
- Vertical fibers - Tidal mark
- Calcification - Calcified zone
- Cement line
- Collagen binds to this
- Cells here and from tidal mark down secrete hydroxyapatite
Vasculature of cartilage
No vessels, nerves or lymphatics
how does cartilage prevent expansion force
Fibers from surface zone steepen and anchor to lamellear bone bellow, holding tension
What does GAG stand for, and how is it made?
Glycosaminoglycan
Made out of repeating units of disaccharides
Disaccharides are two monosaccharides joined together
Examples of GAGs, and their charges
Chrondriotin (-), keratin sulphate (-)
Outline hyaluronic acid
A long GAG, very very long, that has proteoglycans on it and is therefore a proteoglycan complex
Proteoglycans??
A protein core with GAGs bound to it
Where is hyaluronic acid commonly found, and why
In the middle to deep zone or articular cartilage, attached to collagen fibers.
The negative charges of the GAGs on the core proteins draw positive ions (Na+, K+, Ca2+) into the cartilage, and this draws water inwards also due to a change in osmotic gradient
Influx of water in articular cartiage stops when
Unloaded equilibrium is reached. This is when swelling force of water equals tension of collagen
What happens to articular cartilage under compression?
Water is squeezed out
What is the fluid component of articular cartilage?
Water and ions
How do chondrocytes in articular cartilage get nutrients/get rid of waste?
By dissolving water and CO2 in the water
What is an osteophyte
Bone growing in a synovial joint where it shouldn’t be
Layers of articular capsule
Fiberous (outer) and synovial membrane (inner)
Outline what the fiberous layer of the articular capsule is made of
Dense (irregular or regular connective tissue)
Fibroblasts, nerves, few blood vessels etc
Specifically pain and proprioceptive nerves
What is the purpose of irregular dense connective tissue in the articular capsule?
To resist forces from varying directions
Where does the fiberous layer of the articular capsule end
Meets periosteum
Outline the synovial membrane
Has an intima and subintima layer
Loose variable connective tissue
Villi to increase surface area
In subintima layer, there are few fibroblasts, some macrophages, adipocytes, blood vessels, etc
In intima layer, there are synoviocytes, that secrete hyaluronic acid and lubricating proteins
Where are synovial membranes found
Lines the entire joint cavity in absence of articular cartilage
Where does synovial fluid come from?
It is a blood plasma filtrate from the vessels in the subintima layer of the articular capsule
Outline the features of the joint cavity
It is a potential space rather than a cavity
Cartilage on cartilage contact is only about 50%
Very little (max 2ml) synovial fluid
How do muscles create movement
Conversion of ATP into mechanical movement
Functions of muscles
Movement Stability Communication Control of body openings and passages Heat production (over 80% of bodies heat)
What is the region where a tendon joins to bone called
Osteotendinous junction
MTJ
Myotendinous junction
Insertion of muscle
The attachment that moves the most, typically appendicular
Origin of muscle
The attachment that moves the least, typically axial
average width of a myocyte
10/100 micro meters
Zones of a myofibril
Z bands, I bands, A bands
Dark bands vs light bands
Dark bands are A, Light bands are I
What is a fasicle
A group of myocytes
What is a fascile surrounded by
Perimysium
What is a muscle immediately surrounded by
Epimysium
What are myocytes surrounded by (immediately then after)
Basement membrane then endomysium
What are myofibrils surrounded by
Sarcoplasm
What are muscles coated in?
Deep fascia
Where are most of the blood vessels and nerves found in a muscle
In the endomysium within a fasicle
From outside to inside, what are the layers of the muscle
Skin -> Subcutaneous/superficial fascia -> Deep fascia -> Epimysium -> Muscle -> perimysium -> fasicle -> endomysium -> basement membrane -> myocyte
With a microscope, what is the smallest section of a muscle you will be able to see?
Myofibrils
Intermuscular septa
Barrier inbetween muscles
Where deep fascia meets bone is called
Periosteum
How do muscles grow
Hypertrophy
Outline hypertrophy vs hyperplasia
Hypertrophy is the muscle cells getting bigger, with more organelles such as myofibrils forming
Hyperplasia is the growth of numbers of cells
Hypoplasia
Death of cells
Atrophy
Muscles getting smaller in inter-cellular contents
Outline anabolic steriods
Increases the protein synthesis processes in the body, resembles puberty
Outline function of satellite cells
They are myoblasts that sit in the outside of the cell and can multiply, this is why myocytes are a syncytium
Functions of the epi/peri/endomysium
- organisation and scaffolding
- Blood vessels and nerves
- Protect/prevent overstretching
- Distribute force of muscle
How is contraction and distribution of force in muscles even?
Through desmin proteins that link adjacent Z discs together, and through protein complexes that link the outer most myofibril’s Z line/disc to the sarcolemma, basement membrane and endomysium
