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204 > The Physiology Of Bone > Flashcards

The Physiology Of Bone Flashcards

1
Q

Excessive bone formation leads to?

A

Osteopetrosis

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2
Q

Excessive bone resorption leads to?

A

Osteoporosis
Osteopenia
Risk

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3
Q

Cortical bone?

A

Thick hard bone, isn’t organised in spicules

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4
Q

Spicules?

A

Web or mesh

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5
Q

Microscopic bone appearance?

A

Lamellar and woven

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6
Q

Bone is made of?

A

Osteoclasts
Osteoblasts
Osteocytes- maintain bone

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7
Q

Osteoblasts are found?

A

On surface bone

Produce protein component
Acellular matrix
Regulate bone growth and degradation

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8
Q

Osteocytes are?

A

Quiescent mature cells embedded in bone matrix, maintain bone

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9
Q

Osteoclasts responsible for?

A

Bone degradation and remodelling

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10
Q

Organic is?

A

Cells and proteins

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11
Q

Inorganic material?

A

Minerals , ca and PO, when they mix together they make hydroxyapatite

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12
Q

Hydroxyapatite is made up of?

A

Ca and PO

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13
Q

Haversian system runs?

A

Parallel to bone and along long axis of bone

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14
Q

The hydroxyapatite between osteocytes is called?

A

Ground substance

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15
Q

Osteocytes arise from?

A

Osteoblasts, from mesenchyme precursor cell in bone marrow stroma

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16
Q

Osteoblasts are?

A

Post mitotic, most go undergo apoptosis

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17
Q

Osteoclasts are?

A

Multinucleate, oval shaped nuclei, 40-100um

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18
Q

Precursor of osteoclasts?

A

Same as monocytes (haematopoietec stem)

Hence phagocytose and destroy bone matrix and crystals

Secrete acids
Secrete proteolytic enzymes from lysosomes

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19
Q

Where bone resorption occurs its called?

A

Ruffled border

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20
Q

Extracellular matrix is what percent minerals?

A

70

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21
Q

Tensile strength the strength to?

A

Manage being pulled apart

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22
Q

Compressive strength?

A

Able to withstand being bent

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23
Q

Bone is made of?

A

Collagen triple helix- bending
Hydroxyapatite- provide rigidity
( more than 50%)

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24
Q

Extracellular matrix contains?

A

Glycosaminoglyscans - long polysaccharide, highly negative.

Attract water but repel each other. Can resist compression. Fluffy stuff.

Abundant in cartilage

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25
Q

When do growth factors appear?

A

After osteoclasts action, leading to local proliferation and mineralisation

26
Q

Where do osteoclasts resort bone?

A

Howships lacuna

27
Q

How does bone remodelling happen?

A

Osteoclasts break down bone liberating matrix bound growth factors.

This causes osteoprogenitor cells to produce active osteoblasts

28
Q

Difference between compact and cancellous?

A
29
Q

Difference between intramembranous and endochondral bone formation?

A
30
Q

Major factors governing remodelling?

A

Recurrent mechanical stress

Calcium homeostasis

31
Q

Mechanical stress causes?

A

Promotes deposition

32
Q

How does mechanical stress work?

A

Osteocytes and osteoblasts detect stresses, skeleton reflects forces acting on it

In an osteoporotic bones there are more spaces

33
Q

Osteoporosis drug??

A

Bisphosphonates, alendronate looks like pyrophosphate.

Accumulate in bone and are taken up by osteoclasts Work by inhibit osteoclasts mediated bone resorption

34
Q

Osteoporosis drug to encourage bone formation?

A

Teriparatide, portion of PTH, intermittent application activates osteoblasts

35
Q

Drug to prevent osteoclasts maturation?

A

Denosumab, monoclonal antibody targets RANkL

36
Q

Osteopetrosis is a condition that is?

A

Autosomal recessive

37
Q

How does osteopetrosis work?

A

Prevents osteoclasts cannot remodel bone,

Can’t secrete acid due to defective chloride channel or vacuolar proton pump

38
Q

Osteopetrosis happens at?

A

Foramina pressing on nerves.

Brittle bones
Blindness
Deafness
Severe anaemia (run out of bone marrow)

39
Q

Phases of fracture healing?

A
  1. Haematoma and inflammation
  2. Soft callus formation- structural connection (woven bone or fibrocartilage)
  3. Hard callus formation ( lamellar bone replaces woven bone).
  4. Remodelling- trabecular bone replaces lamellar bone, compact bone formed
40
Q

Duration of bone fracture phase?

A

Upper body- 2-3 weeks

Lower body more than 4 weeks

41
Q

PTH and vitamin D causes?

A

Increase in Calcium plasma

42
Q

Calcitonin works by?

A

Made by thyroid c cells
Lowers blood calcium
Used as treatment for osteoporosis

43
Q

Calcitonin is used for treatment of?

A

Osteoporosis

44
Q

What percent of peak bone mass is determined genetically?

A

60-70

45
Q

How does PTH work on osteoblasts?

A

PTH bind on receptor consistently on osteoblasts, puts RANKL on its surface.

RANK receptor on osteoclasts precursor detects in, becoming activated.

46
Q

How to protect from osteoclast activation

A

OPG- decoy receptor therefore prevents RANK binding so less osteoclast activation

47
Q

Where does ca resorption happen at kidney?

A

DCT

48
Q

Negative feedback for preserving calcium plasma level?

A

Bone mobilise ca to plasma

Kidney increase ca resorption in dct

Enterocytes increase calbindin so more absorption

49
Q

Vitamin d3 is formed in?

A

Skin

50
Q

Vitamin D production

A

D3 hydroxylated in liver 25 OH cholecalciferol

In kidney it becomes 1,25 di)H cholecalciferol, calcitriol active vitamin D

51
Q

How does vitamin D cause release of calcium from bone?

A

Stimulates osteoclast indirectly via osteoblasts

52
Q

Causes of low plasma calcium?

A

Pregnancy
Lactation
Kidney dysfunction

Insufficient ingestion of calcium
Rickets

Parathyroid dysfunction

53
Q

Acute hypocalcaemia signs?

A 
Bleeding 
Anaesthesia
Dysphagia 
Convulsions 
Arrhythmia
Tetany
Spasms and stridor
54
Q

Acute hypocalcaemia signs?

A

Chvosteks sign- hit them in face, squeezing of muscles

Trousseau’s sign- carpopedal spasm

Digeorge syndrome

55
Q

Hypocalcaemia makes membrane?

A

More excitable less stable

Sodium is more able to leak through it, causing latent tenany

56
Q

Hypercalcaemia makes membranes more?

A

Stable, less excitable

57
Q

Hypercalcaemia signs symptoms?

A

Asymptomatic
Constipation
Depression and other psychiatric

Abnormal heart rhythms

Coma/ cardiac rest

58
Q

Haversian canal contains?

A

Fluid for maintenance

59
Q

Purpose of glycosaminoglycans?

A

Highly negative, attract water, but they repel each other, fluffy stuff, resist compression

Lots in cartilage

60
Q

Chronic hypocalcaemia results in?

A 
Skeletal deformities
Impaired growth
Short stature
Dental deformities
Increased tendency to bone fractured

204 (58 decks)

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