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Flashcards in Bone Deck (36)
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1
Q

What are the functions of bones?

A

Weight bearing / support
Mineral store
Protection
Blood formation

2
Q

What is the hard bone found on the outside of the bone?

A

Cortical

3
Q

What is the spongy bone called?

A

Trabecular

4
Q

What is the cavity in the bone called?

A

Medullary cavity

5
Q

How is compact bone organised?

A

Compact structures called osteons or haversian systems

6
Q

What type of canals exist in haversian systems?

A

Central haversion canal and horizontal perforating / volkmann’s canals

7
Q

What can be found around a haversian canal?

A

Osteocytes and concentric rings of bone matrix (lamellae) around the haversion canal

8
Q

How does density differ between spongy bone and dense bone?

A

Spongy bone is much less dense

9
Q

What does spongy bone consist of?

A

Network of lamellated trabeculae (a network of intercommunicating spaces)

10
Q

What is the direction of the trabeculae dependant on?

A

The main direction of mechanical forces

11
Q

What are the six types of bones?

A

Flat bone, Sutural bone, Irregular bone, Long bone, short bone, sesamoid bone

12
Q

What are the two types of bone formation?

A

Endochronal (most common type including long bone growth)

Intramembranous (Flat bones of the skull, mandible, maxilla, clavicles)

13
Q

What are the stages of endochronal ossification?

A
Bone forms as cartilage 'model' first
Blood vessels invade the cartilage 
Cartilage is replaced with bone
Cartilage remains in the epiphyseal growth plate
Growth plate eventually ossifies
14
Q

Describe the stages of intramembranous ossification

A

No cartilagenous phase!
Mesenchymal cells develop into osteoprogenitor cells that mature into osteoblasts that start depositing bone.
Residual mesenchymal cells develop blood vessels and bone marrow
This bone formation also occurs in adult cortical bone

15
Q

What makes up bone cells?

A

Osteoblasts, osteocytes and osteoclasts

16
Q

What makes up the extracellular matrix?

A

45% hydroxyapatite crystals
35% collagen type 1
20% Water

17
Q

What properties does the hydroxyapatite confer?

A

Make bones stiff and able to support structures

High strength under compression

18
Q

What properties does collagen give to the bone?

A

Gives the bones some flexibility and reduces the risk of fracture
High strength under tension

19
Q

What ways is bone considered dynamic?

A

Fracture healing and bone density adaptation to high stress (sports)

20
Q

What is responsible for the bone turnover/remodelling?

A

Osteoclasts breaking down old bone

Osteoblasts building new bone

21
Q

What type of membranes exist in the bone?

A

Periosteum and endosteum

22
Q

Where are the osteoblasts created by the osteopreginitor cells?

A

Periosteum and endosteum

23
Q

What is the function of an osteoblast?

A

Produces bone matrix and initiates calcification

24
Q

What is osteoid?

A

Unmineralised matrix

25
Q

When does an osteoblast become an osteocyte?

A

Once it is surrounded by matrix

26
Q

What is an osteocyte?

A

Mature bone found inside lacunae (cavity within bone)

27
Q

What are canaliculi?

A

Connect lacunae to each other - allows communication between cells

28
Q

What are osteoclasts?

A

Multinucleate cells derived from monocytes/ macrophages

29
Q

What is the function of osteoclasts

A

resorb bone matrix

30
Q

What does the extracellular matrix consist of?

A

Mainly minerals, protein, collagen and water

31
Q

Describe the fibres in the extracellular matrix

A

Mostly modified type 1 collagen fibres
Strongly cross linked and large gaps within the fibres
Gaps provide space for hypoxyapatite crystals
Collagen fibre formation is linked to mechanical forces

32
Q

What diseases can result when resorption is greater than formation?

A

Osteoporosis and pagets disease

33
Q

What disease results from a decrease in bone resorption?

A

Osteopetrosis

34
Q

Why is there a loss of bone mass in women after the menopause?

A

Less oestrogen - confers an inhibitory effect on bone breakdown

35
Q

What is responsible for bone density?

A

Genes and the environment

36
Q

What is good for increasing bone mineral density?

A

Resistance and high impact sports