Bone Flashcards Preview

Science for Medicine > Bone > Flashcards

Flashcards in Bone Deck (36)
1

What are the functions of bones?

Weight bearing / support
Mineral store
Protection
Blood formation

2

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

Cortical

3

What is the spongy bone called?

Trabecular

4

What is the cavity in the bone called?

Medullary cavity

5

How is compact bone organised?

Compact structures called osteons or haversian systems

6

What type of canals exist in haversian systems?

Central haversion canal and horizontal perforating / volkmann's canals

7

What can be found around a haversian canal?

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

8

How does density differ between spongy bone and dense bone?

Spongy bone is much less dense

9

What does spongy bone consist of?

Network of lamellated trabeculae (a network of intercommunicating spaces)

10

What is the direction of the trabeculae dependant on?

The main direction of mechanical forces

11

What are the six types of bones?

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

12

What are the two types of bone formation?

Endochronal (most common type including long bone growth)
Intramembranous (Flat bones of the skull, mandible, maxilla, clavicles)

13

What are the stages of endochronal ossification?

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

Describe the stages of intramembranous ossification

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

What makes up bone cells?

Osteoblasts, osteocytes and osteoclasts

16

What makes up the extracellular matrix?

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

17

What properties does the hydroxyapatite confer?

Make bones stiff and able to support structures
High strength under compression

18

What properties does collagen give to the bone?

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

19

What ways is bone considered dynamic?

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

20

What is responsible for the bone turnover/remodelling?

Osteoclasts breaking down old bone
Osteoblasts building new bone

21

What type of membranes exist in the bone?

Periosteum and endosteum

22

Where are the osteoblasts created by the osteopreginitor cells?

Periosteum and endosteum

23

What is the function of an osteoblast?

Produces bone matrix and initiates calcification

24

What is osteoid?

Unmineralised matrix

25

When does an osteoblast become an osteocyte?

Once it is surrounded by matrix

26

What is an osteocyte?

Mature bone found inside lacunae (cavity within bone)

27

What are canaliculi?

Connect lacunae to each other - allows communication between cells

28

What are osteoclasts?

Multinucleate cells derived from monocytes/ macrophages

29

What is the function of osteoclasts

resorb bone matrix

30

What does the extracellular matrix consist of?

Mainly minerals, protein, collagen and water

31

Describe the fibres in the extracellular matrix

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

What diseases can result when resorption is greater than formation?

Osteoporosis and pagets disease

33

What disease results from a decrease in bone resorption?

Osteopetrosis

34

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

Less oestrogen - confers an inhibitory effect on bone breakdown

35

What is responsible for bone density?

Genes and the environment

36

What is good for increasing bone mineral density?

Resistance and high impact sports