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MSS Weeks 3-5 > Bone Cell Biology > Flashcards

Bone Cell Biology Flashcards

1
Q

What is the function of bone?

A
  • Infrastructure - Bone marrow - Specialized connective tissue - bone is calcified extracellular matrix - Reservoir of Ca phosphate
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2
Q

How is Calcium released from bone?

A
  • PTH induces osteoclasts to reabsorb bone and release calcium
  • Calcitonin antagonizes these processes
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3
Q

What are the cells in bone?

A

Osteoblasts

Osteocytes

Osteoclasts

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4
Q

The matrix is made up of __% inorganic and __% organic stuff

A

70%; 30%

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5
Q

What is the mineral component of bone?

A

Hydroxyapatite

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6
Q

What makes up hydroxyapatite?

A

Calcium and phosphorous

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7
Q

What is osteoid made up of?

A
  • Type I collagen
  • Proteoglycans
  • Glycoproteins
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8
Q

What makes bone acidophilic?

A

Type I Collagen

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9
Q

What is the function of glycoprotein in bone?

A

Promotes hydroxyapatite formation

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10
Q

What makes bone hard?

A

Combined hydroxyapatite and collagen type I

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11
Q

What are some differences between bone and cartilage?

A
  • Bone: 70% mineral, 25% water, Type I collagen, Neuronal and vascular structures
  • Hyaline Cartilage: no minerals, 75% water, type II collagen; no neuronal or vascular structures
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12
Q

________ are specialized fibroblasts

A

osteoblasts

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13
Q

What are the two osteoblast specific genes?

A
  • Cbfa-1: transcription factor bone = master gene
  • Osteocalcin
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14
Q

What is the name of the proteins (growth factors) that induce osteoblast differentiation

A

Bone morphogenetic proteins (BMPs)

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15
Q

What do osteoblasts do?

A

Make osteoid - Type I collagen and glycoproteins

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16
Q

How is bone formation completed?

A

Osteocalcin-mediated deposition of calcium within the osteoid

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17
Q

Where are Osteocytes found?

A

Occupy lacunae between layers (lamellae) of bone matrix

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18
Q

What is the half life of osteocytes

A

25 years

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19
Q

How many osteocytes are there per lacuna?

A

1

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20
Q

How are gap junctions formed between osteocytes

A

Cytoplasmic processes penetrate the matrix (through canaliculi) where they join processes of other osteocytes

21
Q

What to Osteoclasts do?

A

Destroy/remodel bone

22
Q

How are osteoclasts developed?

A

Developed from macrophages that fuse together (multinuclear)

23
Q

What is “Howship’s lacunae”?

A

Hollow areas of matrix where osteoclasts reside

24
Q

Why do osteoclasts form a ruffled border?

A

Osteoclasts are polarized and the active side forms the appearance of a ruffled border

25
How are osteoclasts regulated?
Hormones: * Calcitonin = inhibits * PTH = activates * Lysosomes manufacture cathepsin K which is secreted into the microenvironment * Acid is also released into the microenvironment
26
Where are these cell located? Osteoblasts: Osteocytes: Osteoclasts:
Osteoblasts: in the periosteum with smaller numbers in the endosteum Osteocytes: within lacunae of the bony matrix between the periosteum and endosteum Osteoclasts: Mostly found attached to bony matrix on the endosteal side
27
What is the difference between compact bone and spongy bone?
Compact bone - dense, no cavitation Spongy - cavitation \* both look identical microscopically
28
What makes of flat bone? What makes up long bone?
* Flat bone (calvaria) - * 2 plates of compact bone surround spongy bone * Long bone: * Diaphesis: compact with spongy bone lining marrow * Epiphesis: Caps of compact bone around spongy bone
29
Define Osteon
Cylinder with concentric lamellae
30
What are the two perpendicular canals in bone and what do they contain?
Haversian canals and Volkmanns canals They contain blood vessels, nerves, and lymph
31
What are the two ways bone develops?
1. Intramembranous: osteoblasts deposit osteoid onto mesoderm 2. Endochondral: osteoblasts deposit osteoid onto cartilage
32
In order to build bone, what must happened first?
Calcification of cartilage
33
Endochondral development: at the diaphysis -
Osteoblasts invade calcified cartilage - Secrete osteoid leading to ossification
34
Endochondral development: at the epiphyses -
* Same process as at the diaphysis * Articular cartilage remains at ends of bone * Epiphyseal plate cartilage on opposite side of epiphysis - for growth in length
35
How do long bones get long?
Sex steroid hormones go to the pituitary causing the release of growth hormone which leads to the liver's release of somatomedin (IGF-1) which induces proliferation
36
What are the zones of growth in the long bones?
* Zone of proliferation * Zone of hypertrophy * Zone of calcification (basophilic) * Zone of ossification
37
In calcification, what type of collage is present
Collagen II must be replaced by Collagen X for calcification
38
Explain Fracture repair
* Macrophages remove debris * Chondroblasts secrete a callus of hyaline cartilage * Osteoblasts replace cartilaginous calus with bony callus * Primary bone is replaced by lamellar secondary bone
39
What type of procedures are available for bone tissue engineering?
* Bone morphogenetic proteins: BMP-2 and BMP-7 * Adult stem cells (MSCs) that can become osteoblasts * Growth factors or cells (or both) are implanted within biodegradable 'sponges' made of collagen I
40
We get a new skeleton every ___ years
10
41
Diseases of remodeling
* Osteopetrosis: dense heavy bone; osteoclasts lack ruffled border * Osteoporosis: resorption by osteoclasts outpaces osteogenesis leading to hollow fragile bones
42
Osteoporosis prevention and screening?
* Prevention: dietary calcium; vitamin D (improves absorption of calcium) weight bearing exercise * Screening: bone mineral density; compare BMD with young normal subjects every 2-5 years
43
How are osteoclasts produced?
Stromal cells induced by PTH to secrete: * M-CSF - induces macrophage proliferation * RANK-L - induces macrophage differentiation into osteoclasts * OPG - osteoprotegerin antagonizes RANK\_L by binding to its receptor
44
What inhibits osteoblasts? What induces them?
Leptin inhibits BMP induce
45
What inhibits osteoclasts? What induces?
* Inhibited by calcitonin and osteoprotegerin * Induced by RANK
46
What is the PTH paradox?
PTH induces both osteoblasts and osteoclasts - this is because osteoblast formation is favored with spikes of concentration of PTH; constant PTH favors osteoclast formation
47
Anabolic drugs that are pro osteoblast
PTH 1-34 = teriparatide
48
Anti-resorptive drugs = anti osteoclast
* SERMS (selective estrogen receptor modulators) - Raloxifene * Bisphosphonates (Bonivia) * Calcitonin

MSS Weeks 3-5 (22 decks)

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