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Flashcards in Bone Deck (45):
1

What is endochondral ossification?

The replacement of pre-existing hyaline cartilage with bone

2

Most bones of the body develop by __________ ossification

Particularly which sort of bones

Endochondral

Long bones

3

Hyaline cartilage is _______ to become bone

Mineralised

4

What is the middle portion of a bone called?

Diaphysis

5

What is the portion of bone between the middle of the bone and the epiphyseal growth plates called?

Metaphysis

6

What is the end of a bone called? (After the epiphyseal growth plates)

Epiphysis

7

When do the epiphyseal growth plate of long bones disappear? What are these epiphyseal growth plates replaced by?

After growth ends (in adults)

Compact bone

8

In an embryo, long bones begin as a hyaline cartilage template, how do they develop by endochondral ossification?

1) collar of compact bone appears in the shaft (6-8 weeks)

2) a primary ossification centre is formed at the diaphysis
3) central cartilage calcifies
4) artery penetrates the centre and supplies bone depositing osteogenic cells (8-12 weeks)

5) Medulla becomes cancellous bone
6) cartilage forms epiphyseal growth plates
7) secondary ossification centres form at epiphyses

8) epiphyses ossify
9) epiphyseal growth plates move further apart and bone lengthens
(Prepubertal)

10) growth plates replaced by compact bone (mature adult)

9

What are the 3 different type of bone cells?

Osteoclasts
Osteoblasts
Osteocytes

10

When does an osteoblasts become an osteocyte?

Once it is completely surrounded by bone

11

What is the function and a characteristic feature of osteoclasts?

Resorb and deposit bone/useful in bone remodelling

They are multinucleate

12

The synovial membrane contains macrophages to...

Remove debris from a joint

13

What is intramembranous ossification?

The formation of bone from condensations of mesenchymal tissue

14

Which sorts of bones develop by intramembranous ossification?

Flat bones e.g. Skull, pelvic bone, clavicle

15

As well as help in the development of flat bones, intramembranous ossification is important in...

The thickening of long bones

16

What are the stages of intramembranous ossification?

1) MSCs ---> osteoprogenitor cells ----> osteoblasts
2) osteoblasts lay down an EM with a lot of type 1 collagen (osteoid)
3) osteoid mineralises --->bony spicules
4)osteoblasts ---> osteocytes
5) bony spicules ----> trabecullae ----> woven bone
5) replaced by the lamellae of mature compact bone

17

What do osteoclasts release to help in the remodelling of bone?

H+ ions and lysosomal enzymes

18

Where is compact bone found?

Forms the external surfaces of bone

19

What is the structure of cancellous bone?

Network of bony columns

20

What is found between the spaces in cancellous bone?

Bone marrow

21

What is the periosteum?

Connective tissue with blood supply and fibroblasts on the outside of compact bone

22

What is the endosteum?

The connective tissue between the compact bone and cancellous bone

23

What is the structure of compact bone?

Consists of lamellae of bone in circular structures called osteons

24

What is in the centre of an osteon?

Osteon canal containing blood vessels and nerves

25

What do Volkmann's and Haversian canals contain? How do they appear in an osteon?

Blood vessels, lymphatics and nerves

Haversian canals run parallel to the osteon central canal
Volkmann's canals run perpendicular

26

Where are osteocytes in compact bone?

Embedded between lamellae

27

How do osteocytes communicate with each other?

They have slender cytoplasmic processes which reach out to adjacent osteocytes

Connect via gap junctions

28

What is a difference in structure between cancellous and compact bone?

No volkmann's/haversian canals in cancellous bone

29

What is the general % composition of bone?

65% calcium hydroxyapatite crystals
23% type 1 collagen
10% water
2% non collagen proteins

30

Why does bone breakage result in bleeding?

Blood vessels are broken

31

What are the four general steps in bone fracture repair?

1) haematoma formation
2) fibrocartilaginous callus formation
3) bony callus formation
4) bone remodelling

32

Which cells remove dead/damaged tissue when a haematoma forms during a fracture? Which cells remove the blood clot?

Phagocytic cells/osteoclasts

Macrophages

33

What happens in the fibrocartilaginous callus formation stage of bone fracture repair?

New blood vessels enter the fracture site
Procallus of granulation tissue
Fibroblasts ----> chondrocytes and collagen fibres
Hyaline cartilage sleeve formed
Osteoblasts invade fracture site and form spongy bone

34

What happens in the bony callus formation of bone fracture repair?

New bone trabecullae appear
Fibrocartilaginous callus ----> bony callus (cancellous bone)

35

Which forms of ossification are used in the repair of a bone fracture?

Both

36

What happens in the bone remodelling stage of bone fracture repair?

Callus of cancellous bone ---> compact bone (at cortical regions)
Bone is remodelled to original shape by osteoclasts

37

What are the three types of bone grafting?

Autograft
Homograft
Heterograft

38

Which particular type of animal bone works reasonably well in bone grafting?

Calf bones after refrigeration

39

What is osteoporosis? What does it result in?

A metabolic bone disorder where mineralised bone is decreased in mass

Increased susceptibility to fractures

40

What are the most common fractures as a result of osteoporosis?

Fractures of the vertebral bodies and hip

41

Is there a higher risk of osteoporosis in males or females?

Females

42

What are the two types of primary osteoporosis?

Type 1

Type 2

43

Which group is most affected by type 1 osteoporosis? What is the cause?

Post menopausal women
Oestrogen withdrawal ---> increased osteoclasts

44

Which group of people is most affected by type 2 osteoporosis? What is the cause?

Elderly

Compromised osteoblast function

45

What is the recommended calcium intake of postmenopausal women?

800mg/day