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Phase 1 Medicine - Riona > Musculoskeletal physiology > Flashcards

Musculoskeletal physiology Flashcards

1
Q

What are the functions of bones? (7)

A
  • Hold up against gravity
  • Transmits body weight
  • Protects internal organs
  • Determines basic body shape
  • Haematopoiesis (formation of blood cellular contents)
  • Mineral recevoir for calcium & phosphate & lipid storage
  • Acid-base balance
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2
Q

What are the two types of bone?

A

Primary/woven

Secondary/lamellar

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3
Q

What are the two subtypes of secondary bone?

A

Compact

Spongy/cancellous - trabeculae

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4
Q

What are the reasons for bone remodelling? (6)

A
  • Form bone shape
  • Replace woven bone with lamellar
  • Reorientate fibres & trabeculae in favourable direction for mechanical strength
  • Response to loading
  • Repair damage
  • Obtain calcium
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5
Q

What are the 5 types of bone according to shape, and an example of each?

A 
Long - femur
Short - carpals
Flat - skull
Irregular - vertebra 
Sesamoid - patella
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6
Q

What are the differences between the axial skeleton & the appendicular skeleton?

A 
Axial = skull, spinal column, ribs, bones of trunk
Appendicular = limbs, inc scapulae & pelvis
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7
Q

What is the epiphysis?

A

Head of a long bone

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8
Q

What is the diaphysis?

A

Shaft of a long bone

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9
Q

What are the 2 substances make up the composition of bone?

A

Mineral

Matrix

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10
Q

What is the mineral part of bone made from?

A

Hydroxyapatite, crystalline form of calcium phosphate

Adds stiffness & rigidity

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11
Q

What is the matrix part of bone made from?

A

Type I collagen
Provides elasticity
Osteoid

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12
Q

Define ossification

A

The process by which embryonic connective tissue is replaced by bone

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13
Q

How does endochondrial ossification begin?

A
  • hyaline cartilage proformer for bone formation
  • vascularisation of perichondrium (outermost layer of cartilage)
  • mesenchymal stem cells in primary ossification centre gain blood supply
  • stimulated to develop into osteoblasts
  • produced & secrete osteoid
  • congregate at wall of diaphysis, forming bone collar
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14
Q

What stimulates the mineralisation of the osteoid?

A

Chondrocytes in hyaline cartilage send out signals

Forms primary bone as a collar

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15
Q

What results in formation of a cavity in the centre of the cartilage?

A

Mineralisation of bone means nutrients cannot be delivered to chondrocytes beneath it so cell death occurs

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16
Q

What results in the formation of spongy bone inside the cavity?

A

Periosteal bud invasion
Blood vessels & lymphatics to cavity
Also has osteogenic cells (osteoclasts & osteoblasts)

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17
Q

Where do the osteoblasts & osteoclasts work?

A

Osteoblasts in middle/behind osteoclasts to lay down spongy bone
Osteoclasts work at ends of cavity to degrade cartilage

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18
Q

What does the cavity in the centre become?

A

Medullary cavity

Where yellow bone marrow is stored

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19
Q

Where does the degradation of cartilage in the centre of the epiphyses occur?

A

Secondary ossification centre

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20
Q

What causes elongation of bone?

A

Chondroblasts that form hyaline cartilage still working at ends

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21
Q

What do osteoclasts leave at the edges of epiphyses?

A

Articular cartilage

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22
Q

How does intramembranous ossification occur?

A

Mesenchymal stem cells in the middle of connective tissue membranes differentiate into osteoblasts
Produce osteoid that gets mineralised
Flat bones of skill, clavicle, shafts of ribs

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23
Q

What does exercise do to bone formation?

A

Increased strain; increased bone formation

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24
Q

What 3 places does extracellular calcium come from?

A

Absorbed in gut
Reabsorbed from tubule fluid in kidneys
Reabsorbed in bone

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25
Q

What is most of EC calcium in the form of?

A

Free ionised Ca2+ ions

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26
Q

Where is calcium absorbed?

A

Actively - duodenum & jejumum

Passively - ileum & colon

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27
Q

What causes an increase in the amount of calcium?

A

Calcitriol

1,25-dihydroxyvitamin D

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28
Q

What are the 2 ways calcium can be released from bone?

A

Rapidly - exchangeable calcium at surface of bone

Slowly - osteoclasts on bone surface (secrete acid onto bone)

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29
Q

What type of calcium is not filterable?

A

Protein-bound

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30
Q

Where does the majority of calcium reabsorption take place?

A

PCT
Thick ascending tubule
Some in DCT, under hormonal control

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31
Q

Which cells in the parathyroid glands detect calcium & secrete PTH?

A

Chief cells

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32
Q

What type of hormone is PTH & hence where are its receptors?

A

Peptide hormone

On plasma membranes

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33
Q

What does PTH use as a secondary messenger?

A

cAMP

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34
Q

What does PTH do in the kidneys? (3)

A
  • Increase production of 1,25-dihydroxyvitamin D
  • by stimulating activity of 1a-hydroxylane enzyme that produces this from 25-hydroxyvitamin D
  • Increases reabsorption of calcium from tubule fluid in DT
  • Decreases amount of phosphate being reabsorbed
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35
Q

What does 1,25-dihydroxyvitamin D do?

A

Increases absorption of calcium from gut

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36
Q

What does PTH do to bones? (2)

A
  • Stimulates immediate release of calcium from exchangeable calcium on surface of bone
  • Stimulates increase in amount of bone remodelling (osteoclast activity increases to release calcium)
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37
Q

What is calcitonin?

A

Peptide hormone

Antagonist to PTH

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38
Q

What are the 3 main effects of calcitonin?

A
  • Inhibits osteoclast activity
  • Stimulates osteoblast activity
  • Inhibits DCT reabsorption of calcium
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39
Q

How is vitamin D produced?

A
  • UVB radiation hits skin
  • stimulates conversion of 7-dehydrocholestrol into cholecalciferol
  • transported to liver
  • acted upon by 25-hydroxylase enzyme to convert it into 25-hydroxyvitamin D (pro hormone)
  • transported to kidneys
  • acted upon by 1-alpha hydroxylase enzyme into 1,25-dihydroxyvitamin D (active)
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40
Q

What do osteoclasts originate from?

A

Haemopoietic stem cells

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41
Q

What are Howship’s lacunae?

A

Small cavities on the surface of bones where osteoclasts are found

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42
Q

What is the sealing zone?

A

The area where a osteoclast attaches onto the bone

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43
Q

How do the osteoclasts absorb bone?

A

Secrete H+ ions through action of carbonic anhydrase enzymes in cell
Secrete collagenases
Secretions break down bone matrix

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44
Q

What is the role os osteoblasts?

A

To secrete ostoid

45
Q

What do osteoblasts originate from?

A

Mesenchymal stem cells via osteoprogenitors

46
Q

What is the different in nuclei between osteoclasts & osteoblasts?

A

Clasts - large multinucleate

Blasts - uninucleate

47
Q

How are osteocytes formed?

A

Osteoblasts trapped in bone matrix in concentric rings in osteons when lamellar (secondary) bone is formed

48
Q

How do osteocytes receive nourishment?

A

Through small canaliculi that extend from the central canal (Haversian canal) in the centre of the osteon
Slow delivery - limits growth

49
Q

What is RANK-ligand?

A

A protein found on osteoblast cell surface membranes that is able to bind to the RANK receptors on the cell surface membrane of the osteoclast precursors

50
Q

What does the binding of RANK-ligand do?

A

Stimulates osteoclast precursors’ differentiation to osteoclasts

51
Q

Where are RANK-ligands also found?

A

On the cell surface membrane of osteoclasts themselves

52
Q

What is another protein that is similar in structure to RANK-ligand?

A

Osteoprotegrin (OPG)

53
Q

What does the binding of OPG cause?

A

Can bind to RANK receptors
Inhibits RANK-RANK-l pathway as it does not cause differentiation
Reduces osteoclastic activity

54
Q

Define fracture

A

Breach in the continuity of bone

55
Q

What are the two ways in which a fracture can occur?

A

Non-physiological load applied to normal bone

Physiological load applied to abnormal bone (fragility fracture)

56
Q

How is a fracture described? (5)

A 
Site
Pattern
Displacement/angulation
Joint
Skin
57
Q

What is an intra-articular fracture?

A

A joint is involved

58
Q

What are the 4 stages of fracture healing?

A

Haematoma
Inflammation
Repair
Remodelling

59
Q

What occurs during the haematoma stage of healing?

A

Within hours
Bleeding from endosteal & periosteal blood vessels
Blood accumulates around fracture site
Death of cells

60
Q

What occurs during the inflammation stage of healing?

A

Few days
Formation of fibrin clots & neovascularisation (new blood vessels)
Cleaning up of any fragmented/dead tissue by haematopoietic cells (repair cytokines & osteoclasts)

61
Q

What occurs during the repair stage of healing?

A 
Weeks
Formation of a callus
Fibroblasts form fibrous tissue that acts as basis for chondroblasts, which then produce & lay down cartilage
Osteoblasts secrete osteoid
Mineralised into primary bone
62
Q

What occurs during the remodelling stage of healing?

A

Months/years
Woven into secondary
Vascularisation back to normal
No scarring (unique to bone tissue)

63
Q

Define a ligament

A

Fibrous connective tissues that connect bones to other bones

64
Q

Define a tendon

A

Fibrous connective tissues that connect muscles to bones

65
Q

What are 2 of the roles of a ligament?

A

Confer mechanical stability to skeleton

Help guide motion of a joint, preventing excessive motion

66
Q

What are 3 of the roles of a tendon?

A

Provide solid base onto which muscle can insert
Help transmit tensile weight that the muscle is experiencing to the skeleton
Aids in stability of joint

67
Q

What are 4 differences between ligaments & tendons?

A
  • ligaments have less collagen
  • ligaments have more elastin
  • ligament fibres are more randomly organised
  • ligaments receive their blood supply through their insertion sites; tendons can be vascular or avascular
68
Q

What are ligaments & tendons made up of?

A
  • Dense connective tissues that consist of mainly parallel fibres (gives high tensile strength)
  • Have tenocytes
69
Q

What are tenocytes?

A

Fibroblasts that synthesise & remodel the extracellular matrix

70
Q

Why do ligaments & tendons have a poor capacity for healing?

A

Poorly vascularised

71
Q

What is the hierarchal structure of ligaments & tendons?

A
  • 3 procollagen helices bound together to form a tropocollagen
  • multiple tropocollagen bound together to form a microfibril
  • microfilbrils form sub fibrils
  • subfibrils form fibrils
  • fibrils bind together by endotenon to form fascicles
  • fasciles bound by peritenon to form tendon/ligament
  • then surrounded by epithenon
72
Q

What helps to regulate the diameter of a collagen fibre during fibrillogenesis?

A

Proteoglycans

73
Q

What do proteoglycans also do?

A

Keeps fibrils together

Act as lubricant to help the fibres move over one antoher

74
Q

Where is collagen initially synthesised?

A

Fibroblasts

75
Q

What do fibroblasts produce in collagen synthesis?

A

Procollagen molecules

Single stranded polypeptide chains, left-handed helix (alpha chains)

76
Q

What do alpha chains in collagen synthesis come together to form?

A

3 come together to form a right-handed helix

Cross linking occurs between these chains, enhancing strength

77
Q

How is the triple helix of collagen synthesis made into microfibrils?

A

Transported out of cell via secretion vacuoles
Terminal peptides removed to for tropocollagen
Enzyme lysol oxidase forms cross-links to form microfibrils

78
Q

What are entheses?

A

Connective tissue between tendon/ligament & bone

79
Q

What are the 2 types of entheses?

A

Fibrous

Fibrocartilagenous

80
Q

What are entheses innervated by?

A

Proprioceptive receptors & nociceptor endings

81
Q

How are the fibrous entheses formed?

A

Through intramembranous ossification

Calcified part formed by Sharpey’s fibres (calcified collagen fibres) & attach directly onto bone

82
Q

How are the fibrocartilagenous entheses formed?

A

Through endochondral ossification

Gradual change from collagenous ligament to fibrocartilage then into mineralised cartilage on bone

83
Q

What does the load-elongation curve show?

A

The relationship between load applied to ligament/tendon & the elongation it is experiencing

84
Q

What are the 4 regions of the load-elongation curve?

A

1) toe - small increase leads to straightening out of fibres
2) linear - increasing load leads to increasing straightness & stiffness
3) micro failure - deformed to maximum, progressively fail
4) yield pont - complete failure of whole tissue

85
Q

What are the 4 phases of tendon repair?

A

Inflammatory phase
Reparative phase
Remodelling/consolidation phase
Maturation phase

86
Q

What occurs during the inflammatory phase of tendon repair?

A 
Increased vascular permeability
Influx of inflammatory cells
Platelet aggregation
Fibrin clot forms
Acute local inflammation
87
Q

What occurs during the reparative phase of tendon repair?

A 
3-6 weeks
Formation of granulation tissue
Deposition of disordered collagen fibres
Neovascularisation
Fibroblast proliferation
88
Q

When is the remodelling phase of tendon repair?

A

10-12 weeks

89
Q

What occurs during the inflammatory phase of tendon repair?

A

9-12 months
Decrease in cellular & vascular content of repairing tissue
Increase in collagen type I
Becomes more organised

90
Q

What are 4 factors that affect the mechanical properties of ligaments & tendons?

A

Maturation & ageing
Pregnancy & postpartum
Physical training
Immobilisation

91
Q

What are 3 functions of joints?

A

Allow movement of bones
Bear weight
Transfer load to MSK system

92
Q

What are the 3 main structural classifications of joints & what is an example of each?

A

Fibrous - teeth joints
Cartilaginous - intervertebral discs
Synovial - metacarpopharyngeal joints

93
Q

What are the 3 main functional classifications of joints & what is an example of each?

A

Synarthroses - immovable, mostly fibrous; sutures of skull
Amphiarthroses - slightly moveable, mostly cartilaginous; IV discs
Diarthroses - feel moveable, mostly synovial; hip

94
Q

What are the 3 subcategories of fibrous/synarthroses joints?

A

Sutures - between bones of skull
Gomphoses - peg in socket joints, teeth
Syndesmoses - bones connected by cord or sheet, tibia & fibula

95
Q

What are the 2 subcategories of cartilaginous/amphiarthroses joints?

A

Synchondroses - bones connected by hyaline cartilage, ribs & sternum
Symphyses - pads/plates of connecting fibrocartilage, IV discs

96
Q

What is a synovial joint composed of?

A

2 articulating bones separated by a cavity that is filled with synovial fluid

97
Q

What are the characteristics of a synovial joint? (5)

A
  • articular cartilage
  • joint capsule
  • joint cavity
  • synovial fluid
  • reinforcing ligaments
98
Q

What are menisci?

A

Discs of fibrocartilage

99
Q

What is synovial fluid?

A

A filtrate of blood plasma formed by synoviocytes

100
Q

What are 2 functions of synovial fluid?

A

Lubricates bones

Reduces friction

101
Q

What cells line the synovial cavity?

A

Synoviocytes

102
Q

What are the 6 classes of synovial joints?

A
  • ball & socket (hip)
  • condyloid (wrist)
  • gliding (carpals)
  • hinge (elbow)
  • pivot (neck)
  • saddle (MCP)
103
Q

What are the 3 main types of cartilage?

A

Hyaline/articular
Elastic
Fibrocartilage

104
Q

What are the 3 layers of hyaline cartilage?

A

Superficial
Middle
Deep

105
Q

What is made of type I collagen?

A

Skin, tendons, organs, bone

106
Q

What is made of type II collagen?

107
Q

What is made of type III collagen?

A

Reticulate/connective tissue

108
Q

What is made of type IV collagen?

A

Basement membrane

109
Q

What is made of type V collagen?

A

Cell surfaces, hair, placenta

Phase 1 Medicine - Riona (13 decks)

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