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Science for Medicine A (ME2017) > Bones > Flashcards

Bones Flashcards

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1
Q

Describe the structure of compact bone

A

Organised into circular structures called osteons/Haversian systems

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2
Q

What structure lies in the middle of an osteon ?

A

Haversian canal

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3
Q

The less dense bone is known as what?

A

Spongey (trabecular) bone

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4
Q

Describe the structure of trabecular bone

A

Network of lamellate trabeculae filled with bone marrow (no Haversian systems)

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5
Q

Orientation of trabeculae serves what physiology?

A

Directions of main mechanical stress

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6
Q

What permeates the trabecular bone?

A

Blood vessels

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7
Q

What are the names of the two membranes of bones?

A

Periosteum and endosteum

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8
Q

What three specialised cell types make up bone?

A

Osteocytes, osteoblasts and osteoclasts

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9
Q

What is an osteocyte?

A

Mature bone cells found in lacunae (natural depressions)

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10
Q

What is the function of an osteocyte?

A

Not well understood - its suggested that they may maintain the bone matrix and sense mechanical forces

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11
Q

What channels allow communication between bone cells?

A

Canaliculi connect lamellae to each other

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12
Q

What is an osteoblast?

A

Immature bone cell created from osteoprogenitor cells in periosteum and endosteum

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13
Q

What are the functions of osteoblasts?

A

Produces bone matrix and initiates calcification

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14
Q

Unmineralised bones matrix is also known as what?

A

Osteoids

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15
Q

When do osteoblasts become osteocytes?

A

When the bone matrix is fully developed

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16
Q

What is an osteoclast?

A

Multinucleate cells derived from monocytes/macrophages

17
Q

Where are osteoclasts found?

A

Bone surface

18
Q

What do osteoclasts look like?

A

Large cells with ‘ruffled’ edge

19
Q

What do osteoclasts do?

A

Reabsorb bone matrix

20
Q

Where are the structure called where osteoclasts arefound?

A

Howships’ lacunae (pits on surface of bone)

21
Q

Describe the extracellular matrix of bone

A
  1. 45% Hydroxyapatite crystals (complex calcium phosphate crystal)
  2. 35% collagen
  3. 20% water
22
Q

What is the special feature of collagen found in bone?

A
  1. Modified Type I collagen fibres have strong covalent cross links which leave large gaps for hydroxyapatite crystals
  2. Collagen fibre orientation linked to mechanical forces
23
Q

What two types of bone formation are there?

A

Endochondral and intramembranous

24
Q

Which is the most common type of bone formation?

A

Endochondral

25
Q

Describe the process of endochondral ossification (bone synthesis)

A
  1. Bone forms a cartilage ‘model’ first
  2. Blood vessels invade cartilage
  3. Cartilage replaced with bone
  4. Cartilage remains in epiphyseal growth plate - eventually ossifies
26
Q

What is the key difference between endochondral and intramembranous bone development?

A

Intramembranous bone development has no cartilaginous phase

27
Q

Describe intramembranous ossification

A

Mesenchymal cells develop osteoprogenitor cells that develop into osteoblasts that start depositing bone

28
Q

What happens to residual mesenchymal cells?

A

They develop into blood vessels and bone marrow

29
Q

Healthy bone is a balance of what processes?

A

Removal and formation

30
Q

Describe the process of bone turnover

A
  1. Osteoclasts breakdown old bone
  2. Osteoblasts build new bone
  3. Repeat
31
Q

What are the functions of bones?

A
  1. Weight baring
  2. Protection
  3. Mineral store
  4. Blood formation
32
Q

Weight baring functions are achieved how?

A

Minerals make bone stiff (High strength under compression) and collagen gives bone flexibility and reduces risk of fracture (high tensile strength)

33
Q

Name the six types of bone

A
  1. Flat bone
  2. Sutural bone
  3. Irregular bone
  4. Short bone
  5. Sesamoid bone
  6. Long bone
34
Q

What is osteoporosis?

A

Occurs when the process of reabsorption is greater than the process of formation - this results in bone degradation

35
Q

Paget’s Disease

A

Increased reabsorption/formation - causing massive irregularity in bone structure

36
Q

Osteopetrosis

A

Decreased reabsorption of bone

37
Q

What factors can regulate density of bone?

A
  1. Weightlessness - can cause serious loss of bone density
  2. Athleticism - higher bone density
  3. Resistance and high impact sports are effective at maintaining bone density

Science for Medicine A (ME2017) (19 decks)

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