Bones - Part 1

Question 1

What is the extracellular component of bone?

Answer 1

Matrix

Question 2

The Matrix is the extracellular component of bone. What are its 3 components?

Answer 2

1. Osteoid
2. Mineral
3. Inorganic

Question 3

What is the Osteoid component of the Matrix made of?

Answer 3

Type 1 collagen
Glycosamingoglycans
Osteopontin protein

Question 4

What protein is included in the Osteoid component of the Matrix and what is its job?

Answer 4

Osteopontin protein

= Calcium Homeostasis

Question 5

The Inorganic component of the Matrix is hard due to what material?

Answer 5

Hydroxyapatite (calcium and phosphorus)

Question 6

What are the 2 histologic forms of bone?

Answer 6

Woven

Lamellar

Question 7

Which histologic type of bone is produced rapidly and thus what is its correlating Collagen arrangement?

Answer 7

Woven

= Haphazard collagen arrangement => less structural integrity

Question 8

Is woven bone normal in adults?

Answer 8

No

Question 9

Which histologic type of bone is produced slowly and thus what is its correlating Collagen arrangement?

Answer 9

Lamellar

= Collage is parallel and stronger!

Question 10

Which bone cells synthesize matrix and regulate mineralization?

Answer 10

Osteoblasts

Question 11

What are Osteocytes?

Answer 11

Inactive osteoblasts with little cytoplasm

Question 12

What bone cells control calcium and phosphate levels?

Answer 12

Osteocytes

Question 13

How do Osteoclasts look and what is their job?

Answer 13

MULTI-nucleated macrophages

= Bone resorption

Question 14

Long bones undergo what type of development?

Answer 14

Endochondral Ossification

Question 15

Endochondral Ossification starts with what?

Answer 15

Cartilage mold (anlagen)

Question 16

With Endochondral Ossification, how does Radial Growth occur?

Answer 16

New bone deposited beneath periosteum of Diaphysis (midshaft)

Question 17

With Endochondral Ossification, how does Longitudinal Growth occur?

Answer 17

New bone deposited at the bottom of growth plates (epiphyses)

Question 18

Flat bones undergo what type of development?

Answer 18

Intramembranous Ossification

Question 19

Intramembranous Ossification

Answer 19

Mesenchyme directly ossified by osteoblasts

Question 20

What type of growth is seen with Intramembranous Ossification?

Answer 20

Appositional Growth

= Direct deposit of new bone on surface

Question 21

When does peak bone mass get achieved?

Answer 21

Early adulthood after cessation of skeletal growth

Question 22

Usually, when does bone resorption > bone formation?

Answer 22

4th decade

Question 23

What ligand/molecule do Osteoblasts express/secrete?

Answer 23

RANKL is expressed

OPG is secreted

Question 24

What receptor do Osteoclasts express?

Answer 24

RANK

Question 25

If the Osteoblast RANKL binds RANK on Osteoclasts, what will occur?

Answer 25

(+) NF-KB => (+) Osteoclasts => Bone Breakdown

Question 26

If Osteoblast OPG binds RANK on Osteoclasts, what will occur?

Answer 26

Prevents RANKL from binding => Osteoclasts INHIBITED => Building bone

Question 27

What (+) LRP5/6 receptors on Osteoblasts?

Answer 27

WNT

Question 28

What occurs if WNT (+) LRP5/6 receptors on Osteoblasts?

Answer 28

(+) Beta-Catenin => Produces OPG

Question 29

What can (-) the WNT/beta-catenin pathway in Osteoblasts?

Answer 29

Sclerostin

Question 30

What 2 molecules are the main ones that balance bone formation and resorption?

Answer 30

RANK

WNT

Question 31

What 3 molecules help to BUILD bone?

Answer 31

Estrogen
Testosterone
Vitamin D

Question 32

What 3 molecules help to BREAKDOWN bone?

Answer 32

PTH
IL-1
Glucocorticoids

Question 33

What bone cell does M-CSF activate?

Answer 33

Osteoclasts

Question 34

What cascade does M-CSF activate that (+) Osteoclasts?

Answer 34

Tyrosine Kinase Cascade