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Phase 1 > Musculoskeletal System > Flashcards

Musculoskeletal System Flashcards

1
Q

describe the structure of compact bone (3)

A
  • basic unit is an osteon or Haverian system
  • layers of concentric circles (lamellae) laid around a central canal (Haversian canals)
  • canals contain vessels - blood, nerve and lymphatics
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2
Q

where is compact principally found in long bone?

A

diaphyses - middle part

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3
Q

what structure makes up cancellous bone?

A

mesh work of trabeculae - allows space for marrow

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4
Q

where is cancellous bone principally found?

A

epiphises (ends of bone)

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5
Q

what is the material composition of bone?

A
  • 30% organic - type I collagen (tensile strength + flexibility)
  • 70% inorganic - calcium + phosphate salts (compressive strength)
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6
Q

what other structural feature of compact bone provides strength on all sides?

A

collagen is laid in different directions in each lamella

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7
Q

what is the ground substance of bone ECM mainly composed of? what process do these contribute to?

A
  • glycoproteins and proteoglycans

* calcification - increased ion binding capacity

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8
Q

what are osteoclasts? (2)

A
  • derived from haematopoietic stem cells

* responsible for bone reabsorption

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9
Q

what are osteoblasts? (3)

A
  • responsible for bone formation
  • regulate (paracrine action) osteoclastic bone reabsorption
  • derived from mesenchymal cells
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10
Q

what are osteocytes? what proportion of bones cells do they represent?

A
  • possibly sense mechanical loads
  • have dendritic structure for communication
  • responsible for bone remodelling
  • form when osteoblasts are entombed within hard, mineralised bone (ie. initially derived from mesenchymal cells)

• 90% of bone cells are osteocytes

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11
Q

what is the structure of a long bone? (5)

A
  • long tube-like diaphysis
  • medullary cavity at centre of shaft with cancellous bone
  • 2 epiphyses with articulate surfaces for cartilage and joints
  • epiphyseal growth plate between diaphysis and epiphysis until fusion (becomes epiphyseal line)
  • layer of external and internal connective tissue called the periosteum and endosteum
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12
Q

what is the difference between endochondral ossification and intermembranous ossification? when do these processes occur?

A
  • endochondral is the process of bone gradually replacing a cartilage mould (primary and secondary ossification centres at the diaphysis and epiphyses respectively)
  • intermembranous is present in flat bone development in which no cartilage mould is required and bone is laid on top of bone

• primarily occurs during embryogenesis - may also occur during repair

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13
Q

describe the longitudinal growth of bones (6)

A

1 - cartilage proliferates on epiphyseal side of growth plate
2 - produces columns of chondrocytes embedded in matrix
3 - chondrocytes enlarge and hypertrophy
4 - produce alkaline phosphatase to endure calcification of matrix
5 - osteoblasts add osteoid (organic part of bone) onto calcified matrix
6 - deposited trabecular bone is remodelled and incorporated into diaphysis

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14
Q

at roughly what age does the epiphyseal growth plate fuse?

A

25 years

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15
Q

describe appositional growth of bone

A

1 - bone is laid beneath the periosteum
2 - when bone has reached optimal thickness, osteoclasts reabsorb bone
3 - rate of production and absorption is the same, therefore thickness is maintained

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16
Q

what unit carries out bone remodelling?

A

bone multicellular unit - coupled osteoblasts and osteoclasts activity

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17
Q

what is the composition of cartilage (2)

A
  • large unbranched polysaccharide molecules - glycoaminoglycans
  • arranged in association with collagen fibres (mostly CII)
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18
Q

what is the role of GAGs and collagen in cartilage?

A
  • GAGs hydrate the matrix, making it less rigid than bone

* collagen provides mechanical stability (compressive resistance)

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19
Q

what cells are involved with GAGs?

A
  • chondroblasts produce

* chondrocytes maintain

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20
Q

what is the perichondrium? what type of collagen is it made up of?

A
  • covering on most hyaline cartilage (except articulate cartilage)
  • collagen I fibrils
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21
Q

from what cells do cartilage cells develop?

A

mesenchymal stem cells

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22
Q

describe how cartilage forms (5)

A

1 - mesenchymal cells proliferate and become tightly packed
2 - begin to differentiate into chondroblasts
3 - secrete cartilage matrix
4 - as more matrix is laid down cells become les metabolically active and become chondrocytes
5 - chondrocytes occupy lacunae (small cavities) in matrix to maintain it

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23
Q

how can chondroblasts and chondrocytes be distinguished under the microscope?

A

• chondroblasts are larger, have darker cytoplasm and increased Golgi

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24
Q

what are the major GAGs in cartilage? what structure can they form?

A
  • hyaluronic acid
  • chondroitin sulphate
  • keratin sulphate

• joined to aggregate core to form a proteoglycan

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25
Q

what are the features of hyaline cartilage and where is it found? (3)

A
  • collagen II fibres orientated along lines of stress
  • resistant to wear
  • covers surface of most synovial joints due to increased mechanical stress, also present in the epiphyseal growth plate
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26
Q

what are the features of elastic cartilage and where is it found? (3)

A
  • more elastic fibres and lamellae than hyaline cartilage
  • has more resilience and recoil ability
  • found in ear and epiglottis
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27
Q

what are the features of fibrocartilage and where is it found? (2)

A
  • mostly collagen I fibres embedded in fibrocollagenous support matrix
  • found in discs within joints (eg. knee joint)
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28
Q

what is the definition of the extracellular matrix?

A

non-cellular component of tissues and organs

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29
Q

what are the 2 types of ECM?

A
  • interstitial - surround cells, structural ‘scaffolding’ for tissues
  • basement membrane - separated epithelium from surrounding stroma
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30
Q

what are 4 ways that ECM can support / aid tissue?

A
  • structural support (eg. tensile strength)
  • adhesive
  • signalling
  • chemical environment
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31
Q

what are the 2 parts of interstitial ECM?

A
  • fibres (collagen and elastin)

* ground substance

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32
Q

what are the 5 classes of macromolecules associated with interstitial ECM?

A
  • collagens
  • elastin
  • proteoglycans
  • hyaluronic acid (GAG)
  • other glycoproteins
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33
Q

what is the structure of collagen? (amino acid pattern + shape)

A
  • Gly - X - Y repeating pattern

* 3 polypeptide chains forming a triple helix

34
Q

what are the 2 major arrangements of collagen (+ purpose), and what types form each arrangement?

A
  • fibrillar - I, II, III (strength)

* sheet - IV (support or filter in basement membrane)

35
Q

where are the 4 major types of collagen found?

A

I - dermis, tendons, ligaments, bone, fibrocartilage (hard stuff)
II - hyaline cartilage (other hard one)
III - (reticulin) liver, bone marrow, lymphoid organs, granulation tissue (soft stuff)
IV - basement membranes

36
Q

what other molecule is required to form elastin into functional fibres?

A

fibrillin

37
Q

what stain is used to highlight elastin fibres?

A

van Giessen stain

38
Q

what are the 4 types of typical elastin arrangements in the ECM? compare their relative ‘strengths’ and where they are located

A
  • loose, irregular - some strength (lymphoid tissue)
  • dense, irregular - increased strength (dermis)
  • dense regular - max strength (tendons, ligaments)
  • super-specialised - max strength (bone, cartilage)
39
Q

what is ground substance? what is it made up of?

A
  • amorphous, non-fibrous substance surrounding cells

* water and macromolecules (mainly GAGs and proteoglycans)

40
Q

what are the main GAGs found in 1. synovial fluid, 2. cartilage, 3. basement membrane

A

1 - hyaluronic acid (max hydration)
2 - chondroitin sulphate + keratin sulphate
3 - heparan sulphate

41
Q

what are the primary proteoglycan cores in 1. widespread areas (involved in ECM assembly and growth factor regulation), 2. cartilage, 3. basement membrane

A

1 - decorin
2 - aggrecan + syndecan
3 - perlecan

42
Q

what special molecules are involved in the basement membrane? (2)

A
  • integrins - in hemidesmosomes on cell surface connect to

* laminins - act as organiser and maintains the basement membrane

43
Q

how are collagen IV and laminin arranged in the basement membrane?

A
  • assembled separately independent of scaffolds

* links together with indigenous and perlecan

44
Q

what are the 7 functions of the basement membrane?

A
  • support
  • bind to underlying tissue
  • mediate signals between cells and connective tissue
  • determines cell polarity
  • permits flow of nutrients (permeability)
  • path for cell migration
  • barrier to downward growth
45
Q

what are 4 disorders of the basement membrane?

A
  • cancer - epithelial tissue are malignant once BM is breached
  • diabetes mellitus - thickening of BM in glomerulus changes permeability
  • epidermolysis bullosa - attachment of epidermis to BM
  • Goodpastures syndrome - autoantibodies to collagen VI destroy BM in glomerulus and lung
46
Q

describe the synthesis of collagen (2)

A

1 - initially synthesised as procollagen by fibroblasts

2 - modified by glycosylation and hydroxylation

47
Q

describe the synthesis of elastin (4)

A

1 - initially synthesised as tropoelastin by fibroblasts
2 - modified by hydroxylation
3 - has fibrillin scaffold for assembly
4 - made up of cross-linked fibres

48
Q

what are 4 disorders of the ECM?

A
  • Supravalvular Aortic Stenosis (SVAS) - heart defect resulting from faulty elastin
  • Marfan Syndrome - affects connective tissues due to mutations of fibrillin gene: vision problems, aortic defects, abnormally long limbs
  • Ehlers-Danlos Syndrome - affects connective tissues due to mutation in collagen genes (particularly collagen I): hypermobility, fragile + stretchy skin, chronic pain
  • Alpert Syndrome - chronic kidney disease sue to affected glomerulus structure (collagen IV)
49
Q

what is an articulation?

A

where 2 or more bones make contact

50
Q

describe fibrous joints

A

bones connected by dense, fibrous connective tissue

51
Q

what are the functional classifications of fibrous joints? give examples

A
  • synarthrosis: strong and permit almost no movement - sutures, gomphosis (hold teeth in place)
  • amphiarthrosis: permit more movement than synarthrosis - syndesmosis (bones connected by ligaments eg. tibia and fibula)
52
Q

describe cartilaginous joints. what is the difference between primary and secondary?

A

• bones joined by cartilage - allow more movement than fibrous joints

  • primary - united by hyaline cartilage (epiphyseal growth plate, costco sternal joint)
  • secondary - known as symphyses, covered by hyaline cartilage but joined by fibrous cartilage (IVD)
53
Q

what are the functional classifications of cartilaginous joints? give examples

A
  • synarthrosis: synchrondosis (1st sternocostal joint)

* amphiarthrosis: symphysis (articulating bones separated by wedge eg. between pubic bones)

54
Q

what are synovial joints? what is their functional classification?

A
  • bones are not directly joined

* all synovial joints are diarthrosis

55
Q

describe the structure of a synovial joint

A
  • articulated capsule encloses the joint and is lined by synovial membrane
  • has articulated / synovial cavity containing synovial fluid
56
Q

what are the 6 types of synovial joint? give the axises they move on and example locations

A

UNIAXIAL
• pivot: rotation on an axis - atlanto-axial joint
• hinge: flexion and extension - elbow joint
• plane: gliding and sliding motions - acromioclavacular joint

BIAXIAL
• condyloid: permits abduction, adduction, flexion, extension and circumduction - metacarpophalangeal joint
• saddle: saddle-shaped heads with movement in 2 planes - carpometacarpal joints

MULTIAXIAL
• ball and socket - hip and shoulder joint

57
Q

what is the definition of osteoarthritis?

A

a progressive disorder of the joints caused by gradual loss of cartilage, resulting in the development of bones spurs and cysts

58
Q

what are the anatomical features of a joint exhibiting osteoarthritis? (7)

A
  • thickened capsule
  • synovial fluid leakage forming cysts in bone
  • sclerosis (hardening) of subchondral bone (beneath joint)
  • fibrilated cartilage - softening and loss of structure
  • osteophytic lipping - boney overgrowth
  • synovial hypertrophy
  • altered bone contour
59
Q

what changes are exhibited by articulated cartilage in osteoarthritis? (4)

A
  • swelling
  • colour change
  • cartilage fibrillation
  • erosion down to subchondral bone
60
Q

what are features of the pathogensis of osteoarthritis? (4)

A
  • initial increase in water content, then decreased with chronicity (ie. longer time)
  • decreased proteoglycan synthesis
  • decreased collagen cross-linking
  • decreased aggrecan, GAG and hyaluronic acid size
61
Q

what type of joints are most commonly affected by osteoarthritis?

A
  • weight-bearing joints (hip and knee)

* joints of the hand, foot and spine

62
Q

what is the difference between primary and secondary osteoarthritis?

A
  • primary has an unknown cause but related to degeneration over time
  • secondary usually has a traumatic cause
63
Q

what are the systemic risk factors of primary osteoarthritis? (4)

A
  • age over 45
  • being female
  • genetics
  • nutrition (decreased vit C and D)
64
Q

what are the bio mechanical risk factors of primary osteoarthritis? (3)

A
  • obesity
  • occupation - more wight-bearing labour
  • hypermobility
65
Q

what are 4 common causes of secondary osteoarthritis?

A
  • trauma
  • congenital abnormalities
  • occupational hazards (eg. knee joint of footballers)
  • avascular necrosis (sickle cell) and other bone diseases
66
Q

what are the key symptoms of osteoarthritis? (3)

A
  • pain - particularly performing weight-bearing activities
  • short-lived stiffness in morning - improves in 30 mins or less with movement
  • difficulty moving affected joints / doing certain activities
67
Q

what features of osteoarthritis should be checked for in a history? (5)

A
  • pain
  • decreased walking distance
  • sleep disturbance
  • limp (loose hip abductors)
  • stiffness
68
Q

describe how osteoarthritis initially develops (4)

A
  • balance between cartilage production and degradation is lost (net loss of articular cartilage)
  • localised breakdown by chondrocytes
  • variable cartilage loss - irregular surface
  • inflammation of synovium and joint capsule (debris)
69
Q

describe how osteoarthritis progresses in later stages? (7)

A
  • secondary bone changes result from cartilage loss
  • articulation of bone on bone
  • polishing of subchondral bone (eburnation)
  • cyst development
  • cartilaginous overgrowths (calcified = osteophytes)
  • synovial hyperplasia / hypertrophy
  • joint immobility
70
Q

what is the structure of a skeletal muscle fibre?

A
  • multinucleated
  • unbranded
  • striated
  • cells combined to make long continuous fibre
71
Q

what is the sarcolemma?

A

a thin membrane surrounding the muscle fibre - also connects to tendons at either end

72
Q

what 2 proteins primarily make up a myofibril?

A
  • ‘thick’ myosin filaments (dark bands)

* ‘think’ actin filaments (light bands)

73
Q

what do the ends of the actin filaments attach to? what structure runs along this line?

A
  • Z disc

* T tubules

74
Q

what is the A band of a sarcomere? what is the I band? what is the H zone? what is the M line?

A
  • A - contains mostly myosin with some part overlapping with actin
  • I - contains mostly actin, so are lighter than the A band
  • H - brighter central region of the A band where there is no actin overlap (present in relaxed state)
  • M - dark line bisecting the H zone (formed by cross-connecting elements of cytoskeleton)
75
Q

describe how contraction of skeletal muscle is caused (8)

A

1 - action potential travels along motor neurone to nerve endings on muscle fibre
2 - at endings, acetylcholine is secreted
3 - ACh acts on local area of muscle fibre by opening ligand-gated ion channels
4 - Na+ diffuse through channels into muscle fibre causing depolarisation, and opening voltage-gated Na+ channels to initiate AP
5 - depol. propagated along muscle fibre
6 - AP reaches centre of a fibre (cylinder of myofibrils), causes sarcophagi can reticulum to release Ca2+ ions
7 - Ca2+ ions initiate attractive forces between actin and myosin, causing them to slide alongside each other (decrease distance between Z discs)
8 - Ca2+ ions removed by pumps and returned to reticulum to stop contraction

76
Q

describe the cellular structure of a skeletal muscle fibre (6)

A
  • sarcoplasma suspends myofibrils
  • myofibrils arranged into cylinders around each other
  • myonuclei are flattened and pressed against the sarcolemma
  • mitochondria lie between myofibrils
  • ER replaced with sarcoplasmic reticulum (Ca2+)
  • at level of Z discs, there are 2 terminal cisternae with a T tubule between
77
Q

what are T tubules?

A
  • extensions of the cell membrane that penetrate deep into the muscle cell
  • permit rapid transmission of AP into the cell
78
Q

what are the 3 components of the actin filament?

A
  • G actin - units that make up the double helix
  • tropomyosin - molecule that wraps spirally around actin helix -> block myosin binding sites in resting state
  • troponin - 3 subunits in 1 complex
79
Q

what are the 3 subunits of troponin?

A
  • troponin C - receives a conformational change from calcium
  • troponin T - amplifies change along tropomyosin
  • troponin I - has an inhibitory effect on myosin binding sites -> pulls tropomyosin from binding site when shape changes
80
Q

describe actin-myosin interactions during contraction (5)

A

1 - before contraction begins, heads of myosin bind with ATP
2 - heads act as ATPase and energy is stored as head to extends towards actin (ADP and Pi remain bound)
3 - when troponin-tropomyosin complex binds to Ca2+, active sites on actin are uncovered and myosin binds
4 - process of bind causes conformational change in head - tilts towards arm of myosin called power stroke (uses up energy)
5 - ADP and Pi are released from myosin, and new ATP binds, causing myosin head to detach from actin -> new cycle

Phase 1 (14 decks)

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