1
Q
What is bone considered?
A
a special CT with a mineralized matrix
2
Q
What is bone a storage site for?
A
calcium and phosphate (hydroxyapatite crystals)
3
Q
What is the major structural component of bone?
A
Type 1 collagen
4
Q
How does bone affect blood?
A
It regulates blood calcium levels (calcitonin and PTH)
5
Q
Two types of bone structural arrangement?
A
- compact (outside)
- spongy/trabecular (inside)
6
Q
Osteoblast
A
- secretes dentin
- not fully enclosed in matrix
7
Q
Osteoclast
A
- eats up dentin
- degrades and remodels bone
8
Q
Osteocyte
A
- cell inside of the matrix
9
Q
Structural components of dried bone
A
- calcium phosphate (hydroxyapatite crystals) 67%
- collagen 28%
- non-collagenous proteins 5%
10
Q
General Structure of Bone
A
- proximal epiphysis: articular cartilage
- metaphysis: spongy bone with red bone marrow
- diaphysis: medullary yellow marrow
- metaphysis
- distal epiphysis:
11
Q
What surrounds bone?
A
- periosteum
- endosteum
12
Q
What are the 2 layers of periosteum?
A
- outer fibrous
- inner cellular
13
Q
Where are sharpeys fiber found?
A
at muscle entheses
14
Q
What do sharpeys fibers do?
A
anchor muscle (and periosteum) to bone
15
Q
What direction are the fibers of perichondrium and periosteum?
A
Parallel (except at muscle attachments; perpendicular)
16
Q
Mature bone
A
- called lamellar bone
- can be compact or spongey
17
Q
Immature bone
A
- called woven bone
- has more cells and a diffused arrangement
18
Q
Ground bone preparation
A
- loses ALL organic components
19
Q
Demineralized bone preparation
A
- loses ALL inorganic components
20
Q
ID
A
Volkmann’s Canal
21
Q
ID
A
Volkmann’s Canal
22
Q
ID
A
Circumferential Lamella
23
Q
ID
A
Haversian Canal
24
Q
Does spongy bone have osteons?
A
NO
25
Which type of bone is easier to remodel?
Woven/immature
26
Woven vs Immature Images
27
Woven Characteristics
- unorganized lamellar pattern
- more cells per unit area
- more ground substance
28
Mature Characteristics
- lamellar pattern intact
- less cells compared to woven
- less ground substance; more mineralized
29
Where are osteoprogenitor cells found?
- cellular layer of periosteum
- endosteum
- canals
30
Shape of osteoprogenitor cells
- flat and squamous
31
Role of osteoprogenitor cells
- unspecialized “stem cell” for bone
- produce osteoblasts
- can give rise to any cells in bone
32
Origin of osteoprogenitor cells
mesenchymal stem cells
33
Cells of bone labeled
34
What do osteoprogenitor cells differentiate into?
Osteoblasts
35
Structure of osteoblasts
- contain increased amounts of ER, GA, and mitochondria
- allows for syntheis and secretion of bone matrix
36
Function of osteoblasts
- form bone by producing non-mineralized matrix (osteoid)
- regulate osteoclast function
- T1 collagen
- osteonectin and osteocalcin
37
Location of osteoblasts
- metabolically active at bone surface
38
What is the most important molecule for bone development?
Alkaline phosphatase
39
Osteoblastic differentiation?
- Stable beta-catenin plays a major role in inducing cells to form osteoblasts
40
What induces osteoblast differentiation?
- PDGF
- IDGF
41
Osteoclast activation
- Via PTH receptors on osteoblast
42
Osteoclast inhibition
- Osteoblasts can secrete OPG (osteoprotegrin)
- OPG binds to RANKL and inhibits osteoclast activity
43
What stimulates bone production?
Estrogen
44
What inhibits bone (matrix) production?
Glucocorticoids
45
What stimulates bone resorption?
Prostaglandins
46
What inhibits bone resorption?
Estrogen
47
Osteoblast EM
48
Osteoblast EM
49
Bone attributes image
50
Osteocyte origin
Former osteoblasts trapped in matrix form 90% of cells in the mature skeleton
51
Osteocyte structure
- High nucleus to cytoplasm ratio
- Have long cellular processes for communication via canaliculi in the bone
52
Osteocyte function
- CANT DIVIDE (bc theyre enclosed in bone)
- maintain bone and cellular matrix
- important in regulation of calcium and phosphorus in bone
53
Osteocyte signaling
- Stimulated by calcitonin
- Inhibited by PTH
- Communication with osteocytes via gap junctions in canaliculi
54
What anchors osteocytes to canaliculi walls?
tethering fibers
55
What are bone lining cells?
Spindle-shaped cells on the surface of bone
56
Where are bone lining cells located?
Endosteum and periosteum
57
Bone lining cell origin
Mesenchymal stem cells
58
What can bone lining cell yield
- High oxygen and Low strain = osteoblasts
- Low oxygen and Intermediate strain = cartilage
- High strain = fibrous tissue
59
Bone lining cell image
60
Osteoclast function
reabsorb bone
61
Osteoclast origin
myeloid hematopoietic cells from monocyte/macrophage cell lineage
62
Osteoclast image
63
Osteoclast image
64
What is bone resorption
bone matrix breakdown
65
Bone resorption image
66
Bone resorption image
Integrated Exam 2/9
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