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Intercal - Adaption in physiology > Skeletal Physiology and Adaptation > Flashcards

Skeletal Physiology and Adaptation Flashcards

(74 cards)

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1
Q

Functions of bones

A

Protection
Movement
Support
Metabolic
Mineral storage
Hearing

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2
Q

3 factors of the metabolic role of bone

A

Haematopoiesis, blood production
Homeostasis of Ca2+
Defence against acidosis

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3
Q

What is bone the main mineral reserve for

A

Calcium
Phosphorus

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4
Q

5 classifications of bones

A

Long
Flat (sternum, cranium)
Irregular (vertebrae)
Sessamoid (patella)
Short (talus, carpal etc)

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5
Q

5 features of long bones

A

Highly vascularised
Enclosed by fibrocartilagenous periosteum
Articular cartilage at joint surfaces
Red bone marrow (metaphysis)
Yellow bone marrow (diaphysis)

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6
Q

What does red bone marrow contain

A

RBCs

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7
Q

What does yellow bone marrow contain

A

Fat cells

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8
Q

Two types of bone material

A

Cortical - hard outside (80%)
Trabecular - marrow site (20%)

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9
Q

How does intramembranous ossification form

A

A fibrous plate then bone cells differentiation from fibroblasts and haemopoietic precursors

NO cartilaginous phase

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10
Q

Example of a bone type that undergoes intramembranous ossification

A

Flat bone

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11
Q

How does endochrondral ossification form

A

Bone cartilage forms at 13 months
Bone vessels invade the cartilage
Cartilage remains at the growth plates but bone forms elsewhere by osteogenic cells.
Growth plates fuse at the end of puberty.

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12
Q

Composition of bone

A

Water (20%) - heat to get dry weight
Mineral (hydroxyapatite) (50%) - burn to get ash weight
Organic (proteins e.g. collagen) (30%) - dry - ash

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13
Q

What is the bone mineral name and its role

A

Hydroxyapatite forms rigidity

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14
Q

Features of older bone

A

More mineralised
Further from the surface

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15
Q

What happens to bone when only mineral present when weight is dropped on it

A

Disintegrates completely

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16
Q

Collagen type 1 features

A

Triple helix protien
Combine to make fibrils
Fibrils combine to make fibers and then the gaps are filled with mineral bone.

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17
Q

If the bone is only organic what would happen if a weight is dropped on it

A

Would be extremely elastic as no mineral content to give it its rigidity.

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18
Q

Types of bone water

A

Pore water - in haversian canals
Bound water - works with collagen to give elasticity

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19
Q

What happens to water with age

A

Pore increases and bound water decreases

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20
Q

What machine is used for bone composition

A

Spectroscopy

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21
Q

What is the function of osteoclasts

A

Multinucleated cells formed by the fusion of mononuclear precursors - responsible bone degradation

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22
Q

What is the function of osteoblasts

A

Synthesis of new bones

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23
Q

What is the function of osteocytes

A

Osteoblasts who have become embedded within the bone - function as sensors of mechanical load.

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24
Q

Which cells does osteoblasts and osteocytes come from

A

Mesenchymal stem cells

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25
Where do osteoclasts come from
haemopoietic stem cells
26
What is osteoid
Uncalcified bone matrix - formed by osteoblasts
27
How do osteoclasts degrade bone
Form an F-actin ring to secret acid and cathepsin K (enzyme) to break down bone.
28
How long does the bone remodelling cycle take
3 months
29
The 4 stages of bone remodelling cycle
Quiescence - bone linning cells (at rest) Resorption - osteoclasts working to remove one Reversal - synthesis of new bone matrix formation as osteoblasts are recruited Formation - synthesis of new non-mineralised bone and is then mineralised overtime
30
When is bone formation more than resorption in humans
Younger Opposite for older
31
Factors that influence bone mass
Genes Exercise Nutrition Smoking
32
How does osteoporosis affect the bone
Decrease in bone mass Normal mineral and organic content
33
How does osteoarthritis affect bone
Increase in bone mass Decrease in mineral content Increase in organic content
34
Drugs that inhibit bone resorption
Bisphosphonates SERM HRT
35
How do bisphosphonates work
Induce osteoclast death
36
How do SERM work
Acts as oestrogen in bone to reduce osteoclast activity
37
How does PTH stimulate bone formation
Activated Vit D Increases Ca uptake in the gut Increases bone formation
38
How are osteocytes mechanosensitive
Number of cycles Strain magnitute Load distribution Dynamic stimulus is better for bone formation than static load
39
What is released by osteocytes with increased loading
Sclerostin (Decrease of connectivity with age)
40
How to optimise the bone formation
Increase dynamic strain magnitude Increase number of strain cycles/rate Have rest/refractory periods
41
Define Wolffs law
Bone is a dynamic tissue that will adapt to the loads placed on it. Put wolffs law into exam answer
42
What does a DXA scan do
Measure bone density
43
What imaging technique to see trabeculae in vivo
HRpQCT
44
What imaging technique to see trabeculae ex-vivo
Microscopy
45
Why are larger bones less likely to break when bending
The further the bend is from the centre of the bone the greater the strength
46
Why do bones grow more anteriorly-posteriorly and not mediolaterally
Bones grow wider via periosteal formation - this is not symmetrical and there is usually more present anteriorly and posteriorly due to this is where the most forces are present - this keeps them strong but also light As X4 amount of bone would be needed if it grew anteriorly-posteriorly AND mediolaterally.
47
What is disuse osteoporosis
Lack of loading leads to bone loss - Bed rest Space flight Spinal cord injury
48
What is just as important as bone density to its strength
Bone shape
49
What are the two stages of osteoblast formation EXTRA READING - DIRCKX and MAES
Stage 1 - matrix producing osteoblasts - secrete collagen type 1 Stage 2 - mineralizing osteoblasts - secrete osteocalcin (OCN)
50
3 fates of osteoblasts EXTRA READING - DIRCKX and MAES
1 - Apoptosis 2 - matrix-embedded osteocytes 3 - bone lining cells
51
2 markers that form osteoprogenitor cells EXTRA READING - DIRCKX and MAES
RUNx2 Osterix
52
How do stable fractures heal EXTRA READING - DIRCKX and MAES
Intramembranous ossification - osteoprogenitor cells are recruited and differentiate into osteoblasts.
53
How do unstable fractures heal EXTRA READING - DIRCKX and MAES
Endochondral ossification - haematoma releases cytokines which recruit progenitor cells.
54
What controls the formation of collagen and mineralisation EXTRA READING - BRADLEY
ALK Phosphate Osteocalcin etc
55
Other than strength what is another role of hydroxyapitite EXTRA READING - BRADLEY
Can hold on to toxins e.g lead before forming in bone
56
What is the chemical that affects osteocyte connection via its cytoskeleton EXTRA READING - bonewald
Fimbrin - commonly found in high conc at the edges of osteocytes
57
What do osteoblasts do to activate osteoclasts EXTRA READING - bonewald
RANKL expression when feel areas of microfractures --> recruits monocytes to form osteoclasts
58
Where are progenitor stem cells found EXTRA READING
Periosteum inner layer
59
What enzyme do osteoclasts secrete EXTRA READING
Collagenase and hydrochloric acid
60
What does hydrochloric acid form EXTRA READING
Dissolves hydroxyapatite - Calcium and phosphate
61
How do osteoclasts get controlled to prevent excess bone breakdown
Osteoprotegerin binds to RANKL to slow down osteoclasts
62
How does parathyroid hormone affect bone remodelling
PTH released when low Ca so causes bone resorption so decrease bone mass
63
When does bone shape change
Menopause and age to combat the effects of bone loss - to keep bone strength for as long as possible.
64
How does long term bisphosphonates affect bone strength
Decreases fibril and mineral strain therefore --> followings wolffs law --> decreases bone strength
65
How do corticosteroids affect bones EXTRA READING - BRIOT AND ROUX
Impairement of bone formation as they significantly decrease P1NP and ostecalcin (markers for bone formation)
66
How do corticosteroids affect osteoblasts EXTRA READING - BRIOT AND ROUX
Decrease growth hormone and IGF1 so decreases osteoblast function
67
How do corticosteroids affect osteoclasts EXTRA READING - BRIOT AND ROUX
Increase RANK-ligand and decrease osteoprotegerin (inhibitor for osteoclasts) --> longer time for osteoclasts to be active so more bone degradation
68
How does glucocorticoids cause an increase in falls EXTRA READING - BRIOT AND ROUX
Causes GC-induced myopathy which makes muscles weaker
69
Define osteoporosis EXTRA READING
osteoclastic bone resorption not compensated by osteoblastic bone formation
70
3 causes of osteoporosis EXTRA READING
Oestrogen, vitamin D defciency and hyperparathryoidism
71
How does gut biome and age increase the risk of osteoporosis EXTRA READING
With age, disease anf fraility - the gut microbiome changes rapidly. This can cause a a distruption in short chain fatty acids which are used to regulate osteoclast differentiation causing a dysregulation in the abundance of osteoclasts
72
How does the menopause affect bone remodelling EXTRA READING - MENG XIA JI
Menopause causes decrease in oestrogen which affects bone by - 1 - lowering bone sensitivty to PTH 2 - Increasing calcitonin thus inhibiting bone resorption 3 - accelerating calcium resorption from intestine 4 - reducing calcium excretion from kidney 5 - direct affects on bone as there is oestrogen receptors there A loss of oestrogen means a loss of these protective functions
73
What endocrine conditions can cause oseoporosis EXTRA READING - MENG XIA JI
Cushings Menopause Hyperparathyroidism
74
How does oestrogen directly affect bone EXTRA READING - MENG XIA JI
Ostreogen receptors found on osteoclasts and their progenitor cells. When ostrogen decreases this inhibition is lost.

Intercal - Adaption in physiology (11 decks)

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