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Block 4 > Bone and Muscle Physiology > Flashcards

Bone and Muscle Physiology Flashcards

1
Q

What 2 things is connective tissues made from?

A

Cells

Extracellular matrix

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2
Q

What 2 things is extracellular matrix formed of?

Give properties of each

A

Fibrous proteins

  • collagen
  • elastin

Ground substances

  • transparent
  • colourless
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3
Q

What 3 things is ground substance formed from?

Give properties of each

A

Proteoglycans

  • repeated disaccharides (GAG) around a protein core
  • GAG attracts water

Glycoproteins
-allow cells to adhere to the ECM

Water
-attracted by GAG

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4
Q

What provides the rigidity of bones?

A

Mineralised extracellular matrix (hydroxyapatite)

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5
Q

What provides the resilience of bones?

A

Type 1 collagen fibres

part of the fibrous proteins component of ECM, other component is ground substance remember

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6
Q

What is the condition caused by too little bone called?

A

Osteoporosis

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7
Q

What is the condition caused by too much bone called?

A

Osteopetrosis

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8
Q

What is osteoporosis?

A

A complex skeletal disease characterised by low bone density and micro-archeitectural defects in bone tissue, resulting in increased bone fragility and susceptibility to fracture.

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9
Q

Name 5 wider implications of osteoporosis

A

Future #

Pain

QOL

Long term admission

Mortality

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10
Q

Describe the general pathophysiology of osteoporosis

A

Menopause decreases oestrogen levels

Aging decreases replication of osteoprogenitor cells - fewer osteoblasts being made

Aging decreases activity of remaining osteoblasts - less new bone being made

Increases expression of RANKL and RANK on osteoclasts - favours bone re absorption

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11
Q

What scan is used to assess bone mineral density?

A

DEXA scan

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12
Q

What would a normal T score on a DEXA scan be?

A

T score _> 1

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13
Q

What would an osteopenia T score on a DEXA scan be?

A

T score less than -1 but above 2.5

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14
Q

What would a osteoporosis T score on a DEXA scan be?

A

T score <2.5

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15
Q

What is first line management according to NICE in osteoporosis?

A

Bisphosphonates

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16
Q

Name the 2 bisphosphonates on the drugs list

A

Alendronic acid (alendronate)

Resedronate

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17
Q

What is the MOA for bisphosphonates?

A

Bisphosphonates attach to hydroxyapatite binding sites on bony surfaces, especially surfaces undergoing active resorption.

When osteoclasts begin to reabsorb bone that is impregnated with bisphosphonate, the bisphosphonate released during reabsorption impairs the ability of the osteoclasts to form the ruffled border, to adhere to the bony surface, and to produce the protons necessary for continued bone resorption

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18
Q

How does alendronic acid have to be taken?

A

First thing in the morning, half an hour before food, glass of water, sit upright for half an hour

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19
Q

What are the side effects of bisphosphonates?

A

Asymptomatic hypocalcaemia

GI disturbances

Oesophageal reactions (sit upright)

Osteonecrosis of the jaw (larger doses)

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20
Q

What class of drugs is given is bisphosphantes are not tolerated?

Name the drug

A

Selective estrogen receptor modulators

Raloxifene

Does not stimulate breast or uterine tissue, less at risk of CA.

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21
Q

What SC injection can be given to treat osteoporosis?

A

Parathyroid hormone

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22
Q

What is denosumab’s mechanism of action?

How is it given?

A

It is a monoclonal antibody

Acts in a similar way to OPG

Mops up excess RANKL, reduced activation of osteoclasts

Inhibits osteoclast formation, function, survival.

SC injection once every 6 months

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23
Q

Rickets and osteomalacia are characterised by…..

What is the most common cause?

A

inadequate mineralisation of bone

Vitamin D deficiency

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24
Q

Describe Rickets

A

Defective bone mineralisation at the growth plate only affecting children

Widening of the growth plate

Vitamin D deficiency - chondrocytes fail to apoptose after hypertrophy - growth plate remains soft.

Growth retardation

Bony deformities

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25
Describe osteomalacia
Defective osteoid mineralisation affecting adults and children
26
What is a lytic lesion?
Parts of the bone that have been destroyed, usually due to secondary malignancies/metastasis e.g. breast and lung CA
27
What is a schlerotic lesion?
Thickening/hardening of the bone. Stimulation of bone production so the bone is denser Usually secondary to prostate CA.
28
Describe Paget's disease of the bone
Increased bone turnover Increase in osteoclast activity, which increases osteoblast activity. Increased amount of woven bone being laid down. Can have focal or multifocal sites. Results in overgrowth, bowing, pain, fractures and deformity
29
What investigations would you do to diagnose Paget's disease of the bone?
Bloods - Ca, PTH (normal), ALK P (high) X rays Radionuclide bone scans Bone biopsy if malignancy is suspected
30
How do we treat Paget's disease of the bone?
Walking aids Analgaesia Supplements Bisphosphonates Surgery
31
What is osteogenesis Imperfecta?
A group of hereditary disorders characterised by defective production of type 1 collagen. Type 1 - more prone to #, but unlikely to have deformities from them Type 2 - brittle bone disease. Bones can break during labour, can have respiratory compromise, likely to die in the first few years.
32
Which part of the connective tissue determines the tissue's physical properties?
Extracellular matrix
33
Name 2 important fibres that can be present in the extracellular matrix
Collagen Elastin
34
Where is collagen found?
Type 1 - bone, tendons, ligaments Type 2 - hyaline cartilage Type 3 - structural framework of spleen, liver, smooth muscle Good at resisting tensile forces
35
Name some properties of elastin
Major component of elastic fibres Enables stretch and recoil of tissues Usually mixed with collagen to prevent overstretch Found in walls of large arteries, lungs, skin
36
Name 3 characteristics of cartilage
Strong, flexible, semi-rigid Can withstand compression forces (shock absorber) Smooth surface enables friction-free movement
37
Name 3 functions of cartilage
Forms articulating surface of bones Growth and development bones (endochondral ossification) Supporting framework of some organs e.g. walls of airways
38
Name some specialist features of cartilage extracellular matrix
Contains aggrecan - this is a proteoglycan that contains glycosaminoglycans, which are hydrophillic and therefore attract a lot of water to the cartilage Collagen fibres Elastin fibres
39
Name the proteoglycan found in the ECM of cartilage
Aggrecan A proteoglycan that contains glycosaminoglycans which attract water
40
What is the layer surrounding cartilage called? What is special about this outer layer compared to the rest of the cartilage?
Perichondrium - outer fibrous layer - inner cellular layer The perichondrium contains blood vessels: the rest of the cartilage is avascular
41
Why does cartilage take a long time to heal?
Because it is avascular Cartilage cells get their nutrients by diffusion from the perichondrium
42
What do cartilage cells derive from?
Mesenchymal stem cells
43
Outline the formation of a chondrocyte (cartilage cell)
Mesenchymal stem cells differentiate into chondroblasts (cartilage building cells) Chondroblasts are found in the inner cellular layer of the perichondrium Chondroblasts secrete extracellular matrix and get trapped inside lacuna (spaces) Chondroblasts then mature into chondrocytes
44
Name the 2 types of growth cartilage can undergo
Appositional Interstitial
45
Describe the process of appositional growth of cartilage
Surface layers of matrix added by chondroblasts in perichondrium
46
Describe the process of interstitial growth of cartilage
Chondrocytes grow and divide and lay down new matrix. As more matrix is being made, the chondrocytes get pushed away from each other. Multiple chondrocytes can end up occupying one lacuna and the lacuna will get further away from each other Happens in childhood and adolescence
47
Why does cartilage repair badly in adults?
Because most interstitial growth happens in childhood and adolescence May be some regeneration of damaged cartilage from chondrogeneic cells in the perichondrium But if the damage is large or the cartilage has been removed from the perichondrium, the defect will be replaced with dense connective tissue
48
Name the 3 types of cartilage
Hyaline Fibrocartilage Elastic
49
What is the most common and weakest type of cartilage?
Hyaline cartilage
50
Briefly describe hyaline cartilage
Contains short and dispersed type II collagen fibres and large amounts of proteoglycans Has a perichondrium layer (except at articular surfaces)
51
Name 3 places where hyaline cartilage is found
Articular surfaces of joints Costal cartilages Epiphyseal growth plates
52
What is the strongest form of cartilage?
Fibrocartilage
53
Briefly describe fibrocartilage
Contains thick parallel bundles of type I collagen alternating with hyaline cartilage matrix No perichondrium Found in places that need to resist significant forces - insertion points of ligaments/tendons - IV discs - pubic symphisis
54
Briefly describe elastic cartilage
Strong, flexible, resilient Structures that require deformation but can regain original shape Contains elastic fibres and type II collagen fibres Has a perichondrium
55
What is a joint?
Where 2 or more bones articulate
56
Name the 3 types of joints, according to movement, and their characteristics
Synarthrodial joint - fixed no movement Amphiarthrodial joint - slightly movable Diarthrodial joint - freely movable
57
Name the 3 types of joints
Fibrous Cartilaginous Synovial
58
Name the 2 types of fibrous joints Briefly outline their structure
Sutures Syndesmoses Fibrous joints are bones connected by dense connective tissue, containing mainly collagen but no cartilage
59
Give an example of a suture fibrous joint What type of movement does this joint undergo?
Flat bones of the skull Synarthrodial joint - no movement
60
Give an example of a syndesmoses fibrous joint What type of movement does this joint undergo?
Interosseous connective tissue membrane connecting long bones Amphiarthrodial joint - slightly moveable
61
Briefly describe cartilaginous joints
Bones connected entirely by cartilage Can be immovable or slightly movable Primary and secondary cartilaginous joints
62
Describe a primary cartilaginous joint
Hyaline cartilage only Found at epiphyseal growth plates and costal cartilages
63
Describe a secondary cartilaginous joint
Hyaline cartilage lines the bones with fibrocartilage in between IV discs, pubic symphysis, manubriosternal joint
64
Describe 3 characteristics of a synovial joint
Prescence of a joint cavity between the bones, which contains synovial fluid Hyaline cartilage Joint enclosed by a joint capsule with outer fibrous membrane and inner synovial membrane
65
Which layer of the joint capsule secretes synovial fluid?
Inner synovial membrane
66
Describe a bursa
A sac made of synovial membrane containing synovial fluid that reduce friction of one structure moving over another
67
How are synovial joints reinforced? Give an example
Fibroelastic ligaments crossing the joint prevent excessive movements Lateral meniscus of the knee
68
Name the 6 types of synovial joints
Hinge Ball and socket Plane Saddle Pivot Condyloid
69
Briefly outline osteoarthritis
Most common joint disease Loss of articular cartilage +/- bone leading to synovitis
70
List some risk factors for OA
Genetics Age Female sex Trauma Obesity High/low bone density
71
What causes primary OA?
Genetic factors, no precipitating insult
72
What causes secondary OA?
Joint pathology e.g. trauma, infection, joint defects
73
Draw out the pathophysiology of OA
See slide 36 of joint disease lecture and footnotes
74
What 4 pathological changes would you see on an X ray in someone with OA?
Joint space narrowing - asymmetric Subchondral cysts and sclerosis Osteophytes Malalignment
75
List some signs and symptoms of OA
Joint stiffness Joint pain Functional limitation Rest/night pain Restricted movement Crepitus
76
What are the nodes called on the hands that are visible in OA?
Herberden's nodes

Block 4 (11 decks)

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