Bone

Question 1

2 aspects of bone ECM

Answer 1

1. mineral

2. Organic

Question 2

Features of bone mineral

Answer 2

• 70% of wet weight
• provides rigidity and mineral storage
• Calcium and phosphorous

Question 3

Features of bone organic

Answer 3

• osteoid
• 30% of wet weight
• provides resilence

Question 4

Content of osteoid

Answer 4

• 90-95% is type 1 collagen
• glycoproteins
• proteoglycans

Question 5

3 types of bone cells

Answer 5

1. Osteoblasts
2. Osteoclasts
3. Osteocytes

Question 6

Features of osteoblasts

Answer 6

1. from progentor cells
2. at surface of bone matrix
3. produce and calcify osteoid

Question 7

Gene resp. for osteoblast dev.

Answer 7

CBFA1

Question 8

Features of osteocytes

Answer 8

• from osteoblast that were surrounded - in lacuna
• connected via canaliculli
• maintains bone matrix

Question 9

Features of osteoclasts

Answer 9

• from bone marrow
• multinucleated
• breaks down bone

Question 10

depressions for osteoclasts

Answer 10

howships lacunae

Question 11

Wolf’s law

Answer 11

Bone - use it or lose it

Question 12

Mech. of Ca increase

Answer 12

If Ca down > PTH up > osteoctyes osteolysis

AND > PTH up > osteoblast upreg CSF > more clast number and activity

Question 13

2 types of bone

Answer 13

1. spongy (cancellous)

2. compact

Question 14

Feat. of spongy bone

Answer 14

• crossbridging of spicules adds strength
• org. of spicules reflects stress direction
• bone marrow filles spicules

Question 15

locations of spongy bone

Answer 15

irregularly shaped bones and epiphyses of long bones

Question 16

feat. of compact bone

Answer 16

• forms bone periphery

- osteocytes array in Haversian systems

Question 17

location of haversian systems (osteon)

Answer 17

• parallel to axis of long bones

Question 18

contentsof haversian canals (5)

Answer 18

1. vessels
2. nerves
3. osteoblasts
4. conn. tissue
5. progenitor cells

Question 19

what lies between rings of osteocytes

Answer 19

lamellae - adds to strength

Question 20

function of multidirectional collagen fibers in osteo

Answer 20

resists torque forces

Question 21

locations of woven bone

Answer 21

sites of rapid decomp. - breaks, young bones

Question 22

feat. of woven bone

Answer 22

not in osteons - more random configuration

Question 23

6 basic parts of bone

Answer 23

1. periphery - compact bone
2. diaphysis - the shaft - think compact bone collar with fat inside
3. metaphysis - wide part of shaft, begins to be filled with red marrow
4. epiphysis - the end - compact bone out with spongy inside
5. periosteum - dense irregular tissue on ext. surface
6. endosteum - thin layer of CT lining marrow cavity

Question 24

Path of intramembranous ossification

Answer 24

prog. cells>CBFA1>osteoblast>secrete matrix>osteocyte>spicules enlarge>compact bone>some vessels trapped> haversian canals

Question 25

main feature of endochondrial ossification

Answer 25

begins with hyaline cartiledge which is replaced

Question 26

steps of endochondrial ossification

Answer 26

1. chondrocytes at center hypertrophy>calcification
2. osteoblast dev. from prog. cells>bone collar
3. chondrocytes secrete VEGF>penetration of vessels
4. osteoclastic breakdown of cart.
5. prog. cells in CT accompany vessels>osteoblasts
6. vessels branch toward end cart.
7. process repeats at 2ndry centers
8. tips of spicule trimmed by clasts to open up diaphysis
9. spicules at end of bone remain, but will be turned to bone

Question 27

how bones grow width

Answer 27

• intramembranous ossification
• blasts diff. on outside to make new collar
• clasts work on inside to thin collar

Question 28

how bones grow length

Answer 28

• At epiphyseal cart. / growth plate

- cart. grows interstitially and replaced by bone

Question 29

5 zones of epiphyseal plate

Answer 29

1. zone of reserve - quiet chondrocytes attaching plate to bone
2. zone of proliferation - rapid prolif. @ right angle to length of bone
3. zone of hypertrophy - chondrocytes enlarge and begin to lay down matrix between them
4. zone of calcification - marix begin to calcify and chondrocytes apop.
5. zone of ossification - blood vessel penetrate on diaphyseal side