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oneb Flashcards

1
Q

Functions of bone

A
  • Support
  • load bearing
  • protection (e.g. skull, ribcage)
  • Attachment for muscles/levers for motion
  • Storage of calcium and phosphate
  • Contains bone marrow – important for haematopoiesis
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2
Q

What is bone an example of

A

cONNECTIVE TISSUE

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3
Q

What is structure of bone

A

, consisting of cellular component and ECM mineralised by deposition of hydroxyapatite (basic calcium phosphate)

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4
Q

What is property of bone

A

is resistant to tensile (doesn’t shatter) and compressive forces

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5
Q

Why has bone got good tensile strength, how to prove this

A

Collagen

Heat, denature collagen, shatter bone

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6
Q

Why has bone got compressive strength, evidence

A

Hydroxyapatite crystals

Add acid, demineralise, bone becomes flexible

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7
Q

Why is bone remodelling important

A

enables bone shape to be maintained during growth and allows fracture healing.

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8
Q

What can fibroblast like precursor cells give rise to

A

Osteoblasts, adipocytes, myocytes, chondrocytes

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9
Q

Where are osteogenic cells derived form mesenchymal tissue (undiff and pluiripotent) found in adults. Why are they needed

A

Periosteum and endosteum

Important for remodelling, growth and repair of bones by providing osteoblasts when needed

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10
Q

Cells involved in bone remodelling

A

Osteoblast, osteoclast, osteocyte

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11
Q

What do osteoblasts do

A

secrete osteoid – organic component of bone, initially uncalcified but rapidly becomes mineralised, as you get further away from osteoblasts, by deposition of hydroxyapatite

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12
Q

When are osteoblasts recruited

A

When bone needs to grow

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13
Q

What do osteoclasts do

A

bone removal– important in bone remodelling (they resorb bone), large multinucleated cells macrophages which resorb bone through acid and protease secretion, forming Howship’s lacunae which are depressions of bone surface

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14
Q

What are Howship’s lacunae

A

depressions of bone surface when resorption has occurred.

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15
Q

What are osteocytes

A

preserve bone matrix, sit in lacunae surrounding bony matrix

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16
Q

2 types of bone formation

A

Intramembranous ossification, endochondral ossification

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17
Q

Where does intramembranous ossification occur

A

Flat skull bones, mandible, maxilla, clavicle

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18
Q

What is different about intramembranous ossification

A
  • Bone formation from connective tissue/bone matrix (not cartilage); bone matrix produced by osteoblast
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19
Q

Steps in intramembranous ossification

A

1) Osteogenic progenitor cells differentiate into (mesenchyme which differentiate into) osteoblasts forming ossification centre
2) Osteoblasts secrete osteoid which is mineralised by hydroxyapatite deposition, calcified bone engulfs osteoblasts, they are trapped in matrix becoming osteocytes
3) Spongy bone formation – trabeculae form around blood vessels, leaving pores in which red bone marrow appear later.
4) Peripheral osteoid condenses to form compact bone around spongy bone

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20
Q

Sum up endochondral ossification

A

, initial hyaline cartilage that continues to grow then is calcified by chondrocytes

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21
Q

Describe steps in endochondral ossification

A
  • Periosteum forms around hyaline cartilage.
  • Osteoblasts formed by osteogenic cells secrete osteoid on outside of cartilage, lay down bone, forming compact bony collar.
  • Inner cartilage ossifies, forming primary ossification centre in diaphysis – now impermeable to nutrient diffusion so deteriorates, forming cavities
  • Vessels in periosteum pass through bony collar invading inner cartilage via nutrient foramen through which osteoclasts, osteoblasts also pass.
  • Remaining cartilage broken down by osteoclasts
  • Osteoblasts secrete osteoid forming trabeculae (spongy bone)
  • As this process continues, medullary cavity and diaphysis undergoes elongation and appositional growth.
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22
Q

What’s the difference between second ossification centre and primary

A
  • Spongy bone formed instead of compact
  • Layer of hyaline cartilage remains on ends of long bone
  • Epiphysial growth plates do not mineralise until maturity, allowing long bone growth until adulthood.
    Epiphysial plate made of cartilage, cartilage grows and divides so more cells on under side laid down and bone shaft length increases
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23
Q

When does secondary ossification occur, and where

A

Just before birth, at epiphysis

24
Q

What are the different zones in growing long bone

A

1) Zone of resting cartilage
2) Zone of proliferation
3) Zone of hypertrophy
4) Zone of calcification
5) Ossified bone

25
Q

Pneumonic to remember zones of growing bone

A 
Ryan
Plays
Harp
chords
Oi
26
Q

What happens in zone of hypertrophy

A

chondrocytes mature and enlarge

27
Q

What happens in ossified bone

A

calcified cartilage on diaphyseal side of plate is replaced by bone

28
Q

What happens in resting zone of cartilage

A

cartilage attaches to epiphysis

29
Q

What happens in zone of proliferation

A

new cartilage produced on epiphysial side of plate as chondrocytes divide and form stacks of cells (all growth upwards)

30
Q

Zone of calcification

A

cartilage matrix is calcified and ossified by osteoblasts, mechanism for long bones growing.

31
Q

What happens in osteoporsis

A

: imbalance: bone breakdown>bone formation. Due to too much osteoclast activity or too little osteoblast activity. So amount of bone retained decreases

32
Q

How do bones remodel

A
  • Force/stimulus to remodel – perceived by osteocyte or periosteal osteoblasts.
  • Osteoclasts recruited and remove unwanted bone then die
  • Osteoclast replaced by osteoblasts which are recruited forming new bone then becoming inactive bone lining cells
  • Adds new bone/makes bond stronger.
33
Q

What is appositional bone growth

A

growth or increase by the gradual accumulation of additional layers or matter . The growth in diameter of bones around the diaphysis occurs by deposition of bone beneath the periosteum.

34
Q

Role of osteoblast in appositional growth

A

secrete osteoid against the shaft of the cartilage model

35
Q

Names for spongy bone

A

Trabecular
Spongy
Cancellous

36
Q

2 types of secondary bone

A

Spongy

Compact

37
Q

Describe roles of spongy and compact bone in long bone

A

Spongy forms interior and epiphyses of long bones and surrounded by outer layer of denser and stronger compact bone, which forms most of outer layer of diapysis .

38
Q

Describe trabeculae of spongy bone and compact bone

A

Trabeculae of cancellous bone attached to overlying compact bone at right angles to resist compressive forces

39
Q

Describe cavities in spongy bone

A

Many interconnecting cavities

40
Q

Benefit of spongy bone

A

Forms the interior and epiphyses of long bones (so bone light enough to be moved by muscle)

41
Q

Benefit of compact bone

A

of denser and stronger compact bone, which forms most of outer layer of diapysis and provdes strength (strong cyclinders in shafts of long bone)

42
Q

Structure of spongy and compact bone in flat bones

A

Cancellous bone sandwiched between 2 plates of compact bone

43
Q

Describe primary/woven bone

A

collagen fibres in irregular arrangement with high number of osteocytes and little mineralisaton

44
Q

Where Is primary bone found

A

Tooth socket

45
Q

What happens to woven bone in adults

A

Replaced by secondary bone

46
Q

Describe secondary bone

A
  • Formed as Haversian system/osteon canal along length of diaphysis
  • . Collagen fibres arranged in lamellae/rows. Often arranged around central canal in concentric fashion
47
Q

Where are osteocytes found in secondary bone

A

between concentric layers of lamellae in lacunae (i.e. around each layer).

48
Q

What does central/haversian canal in secondary bone contain

A

neurovascular bundle and loose connective tissue (lamellae on outside of canal)

49
Q

Why do osteocytes need cytoplasmic projections

A

Bone mineralisation prevents diffusion of nutrients and waste products. Instead osteocytes extend cytoplasmic processes into canaliculi (channels within bone containing extracellular fluid) allowing exchange of nutrients and waste products between bone and blood and communication between osteocytes.

50
Q

Describe how osteocytes are linked

A

by canaliculi and gap junctions. Projections of osteocyte connected by gap junctions form network of force sensors in canaliculi throughout the bone, connected to osteoblasts

51
Q

How can osteocyte stimulate bone remodelling

A

Projections of osteocyte connected by gap junctions form network of force sensors in canaliculi throughout the bone, connected to osteoblasts. Osteocytes can therefore communicate when force applied, sense lines of stress and stimulate remodelling to make bone stronger.

52
Q

Role of yellow and red bone marrow

A

Red bone marrow helps produce blood cells. Yellow bone marrow helps store fat.

53
Q

When do epiphysial growth plates mineralise, what’s the consequence

A

Epiphysial growth plates do not mineralise until maturity, allowing long bone growth until adulthood.

54
Q

How are osteocytes formed

A

Osteocytes are simply osteoblasts trapped in the matrix that they secrete

55
Q

How does epiphysial plate allow bone shaft length to increase

A

Epiphysial plate made of cartilage, cartilage grows and divides so more cells on under side laid down and bone shaft length increases

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