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Year 1 - Semester 2 > Locomotor > Flashcards

Flashcards in Locomotor Deck (68)
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What is aggrecan

Main proteoglycan in cartilage


Resists compressive force


What are the three types of cartilage

Articular on movable joints to cushion, reduce friction (along with synovial fluid)
Spread load and resist compressive forces
Collagen II forms an irregular basketweave pattern in ECM
In joints, larynx, trachea, bronchi, ribs

Connects hyaline cartilage to tendon/ligament
Parallel bundle of collagen I fibres to resist tensile strength
Intervertebral discs and meniscus of knee

Elastic - allows flexibility rather than support
External ear, epiglottis


What is an osteon

Concentric layers of bone with a central haversian canal carrying blood vessels and nerves along the long axis of the bone


What are Volkmann's canals

Channels for blood which are s perpendicular to the Haversian canals which supply them from the periosteum


What is the difference between lamellar bone and woven bone

Woven bone is not arranged regularly and is weaker, being produced when bone is laid down rapidly


How is bone formed

Collagen matrix laid down then calcium apatite then hydroxyapatite
Vitamin D dependent


What are the different parts of a bone called

Ends are epiphysis

Middle is diaphysis

Between them is the metaphysis


What are osteoprogenitor cells

Precursors to osteoblasts



Lay down new bone matrix

Regulate osteoclast differentiation and action



Resorbs bone by secreting acid and proteases.

RANK ligand increases formation and activity but can be mopped up by osteoprotegrin



Mature osteoblasts entombed in bone matrix lacunae

Regulate bone remodeling when signalled mechanically or via hormones.

Long processes connect to other cells


What are bone resorption signals


Sclerostin - inhibited by mechanical loading

Parathyroid hormone - stimulated when blood Ca is low to release from bone


What is the apophysis

Where bone attaches to tendon


What is ossification

Deposition of osteoid

Intramembranous - deposition on mesenchymal cells within a fibrous membrane to increase bone thickness. This matrix is mineralised as usual and osteoblasts are embedded to form osteocytes - repairs fractures

Endochondral - deposition in cartilage framework to lengthen bones - produces most of the skeleton


Secondary ossification

Endochondral ossification of epiphysis



Mutated FGF3 receptor leads to reduced chondrocyte growth --> short stature


What influences remodelling

Mechanical load, biological hormones, calcium and cytokines


What are the stages of remodelling

Activation - lining cells expose bone and secrete collegenase. Ocytes make RANKL to recruit osteoclasts

Resorption - osteoclasts borders become ruffled and secrete acid and proteases, then die by apoptosis

Formation - osteoblasts differentiate and lay down down osteoid in cavity then become osteocytes

Mineralisation - calcium laid down (promoted by high Pi/PPi ratio - phosphate - pyrophosphate)
Inhibited by osteopontin


Protective factors

Oestrogen inhibits osteoclast activity, recruits osteoblasts and is a RANKL antagonist

Calcitonin opposes PTH by inhibiting osteoclasts to decrease serum calcium


Describe fracture healing

Macrophages remove debris
Fibrin clot
Inflammation and granulation tissue
Callus formation ( collar of cartilage and bone surrounding fracture to stabilise outer edges of bone)
Ossified to woven bone

Direct fracture repair - no callus formation but healing is simply an extension of remodelling giving rigid fixation
Pins may be necessary to immobilise bone for healing

Mechanotransduction - the conversion of mechanical stimulus into a biological response


Describe synovial joints

Capable of wide range of movement
Held in a fibrous synovial joint capsule with an inner membrane lining (synovium)
Ligaments may be internal or external to this
Bone ends covered in hyaline cartilage and between them is synovial fluid - capillary exudate and glycoproteins


Connective tissue disorders

Marfan - autosomal dominant - mutated fibrillin 1- long extremities,joint hypermobility, aortic rupture

Scurvy- vit c deficiency - fragile blood vessels, haemorrage, tooth/gum damage, poor health

Osteogenesis imperfecta I - reduced collagen I

Osteogenesis imperfecta II - abnormal collagen I

Ehlers-danlos syndrome IV - autosomal dominant, reduced collagen III, complicates pregnancy

Other ehlers-danlos - disrupted stages of collagen synthesis


Describe osteoarthritis

Multifactorial chronic degeneration of articular hyaline cartilage

Pain that worsens on joint use, loss of movement range, bone/soft tissue swelling, tenderness and creaking joints

Loss of collagen through chondrocyte matrix metalloproteases is irreversible to need to prevent this

Collagen II matrix damage leads to increase cartilage hydration which makes it weak.

Decreased PG concentration and chondrocyte death/proliferation indicates damage

Can be abnormal load on normal cartilage or normal load on abnormal cartilage

Loss of joint space is observed, form cysts and osteophytes and subchondral sclerosis.

Large weight bearing joints and distal and proximal inter-pharyngeal joints are most affected


Rheumatoid arthritis

Autoimmune disorder attacks synovial membrane

Synovial fluid becomes turbid from neutrophils

Proliferation of the synovium forms a pannus of granulation tissue over articular cartilage which cuts off its nutritional supply

Erosion of cartilage via MMPs

Scar tissue between the bone ends can ossify and immobilise the joint - ankylosis

Ulnar deviation, tendon and ligament rupture, soft tissue swelling. Pain and stiffness recede on use and inflammation tends to be symmetrical and peripheral.
Especially in small joints - not distal inter-pharyngeal joint

Loss of joint space. ESR and CRP are raised

Three times more in females



Bone resorption exceeds formation - lower bone density

Result of age, reduces exercise, oestrogen deficiency, diet and corticosteroids

Can cause kyphosis

Occurs most frequently in high trabecular content bones - femur head, vertebrae or radius

Dexa scans give a t score for bone density
osteopenia is -1 to -2.5
Below -2.5 is osteoporosis


Pagets disease

Increased resorption and formation leading to persisting woven structure and therefore weak bones

Deformities, fractures, pain and nerve compression

Autosomal dominant



Vit D deficiency decreases calcium absorption and therefore epiphyseal mineralisation



Infection of bone leaving to inflammation which often affects growth plates in children



Airway - obstruction needing removed, oxygen support needed

Breathing - observation of patient colour, breathing effort, injuries, vital sounds, symmetry and chest sound

Circulation - pulses and capillary refill

Disability - assess neurological function with Glasgow coma scale or AVPU plus temperature and blood glucose

Exposure - keep patient warm and check for any missed injuries


Glasgow coma scale

Eyes < 4
Verbal < 5
Motor < 6