MSK Module 1B Flashcards
(65 cards)
1
Q
All connective tissue is composed of:
A
- Cellular component
- Extracellular matrix (with a non-fibrous and fibrous component)
2
Q
Bone tissue consists of:
A
- Cellular component (osteoblasts, osteocytes, osteoclasts)
- Matrix component (collagen, proteoglycans, BMPs, glycoproteins, etc.)
3
Q
Cell types found in bone:
A
Osteoblasts
Osteoclasts
Osteocytes
4
Q
What do osteoblasts produce?
A
- Type 1 collagen
- Non-mineralized bone matrix (osteoid)
5
Q
Function of osteoblasts
A
Formation of new bone:
- Produces substances involved
- Facilitates mineralization of osteoid to complete the process
6
Q
When is an osteoblast considered an osteocyte?
A
Once the osteoid (surrounding bone matrix) is mineralized
7
Q
Osteoblasts are located along:
A
- Trabecular surfaces
- Inner surface of Haversian canal
- Inner surface of periosteum
8
Q
Osteocytes are formed from:
A
Osteoblasts
9
Q
Where are osteocytes located?
A
Lacunae (small cavity)
10
Q
Osteocytes make up approx. ___% of cells in mature human skeleton
A
90
11
Q
Are osteocytes active or inactive?
A
Active in monitoring/maintaining bone status
12
Q
Functions of osteocytes
A
- Stimulate remodeling process
- Serve as mechanism for mechanical stimulus to bone
- Maintain homeostasis of the mineralized bone
13
Q
Where are osteoclasts located?
A
Howship’s lacunae
depressions seen in microscopic view that represent areas of bone resorption
14
Q
How do osteoclasts resorb bone?
A
- Secrete acid and lytic enzymes to dissolve surrounding bone
- Elements of bone are resorbed into ossteoclast at base of microvilli
- Releases bony elements into capillaries to be recycled
15
Q
What happens to an osteocyte after it is resorbed by osteoclasts?
A
Either degenerates or becomes dormant until needed again
16
Q
What is bone matrix composed of?
A
Type 1 collagen (90%) Proteoglycans BMP (bone morphic protein) Glycoproteins Osteocalcin Bone albumin GFs Bone minerals
17
Q
What is Type 1 collagen’s function within bone?
A
- Tensile strength of bones
- Weight bearing (compressive) strength
18
Q
What are proteoglycans? Function?
A
- Part of bone matrix
- Large polysaccharides attached to protein
- Located b/w collagen fibers
- Plays role in calcification/fluid balance by attracting calcium
19
Q
Function of bone morphic proteins (BMP)?
A
- Promote formation of osteoblasts from stem cells
- Promote osteogenesis in osteoblasts
- Promote bone repair
20
Q
Function of glycoproteins in bone?
A
- Assist in collagen fiber formation
- May assist in calcification
21
Q
What is osteocalcin?
A
- Part of communication b/w osteoblasts and clasts
- Produced by osteoblast
- Promotes osteoclast activity
22
Q
What does bone albumin do?
A
- Attracts fluids and maintains fluid balance in bone
- Transports hormones, ions, other metabolites to/from bones
23
Q
What do growth factors (GFs) do in bone?
A
Play role in differentiation, activation, growth, and turnover of bone (and other tissue)
24
Q
What is calcium hydroxyapatite (HAP) and what does it do?
A
- Bone mineral
- An insoluble crystal that deposits within the collagen fibers
- End stage of calcium crystallization for mineralization
25
Bone multicellular unit
- Cluster of cells that breakdown an area of bone surface and then fills it with new bone
- Multiple BMU clusters are activated/inactivated at any given point in time and in different locations
26
6 steps of bone remodeling
1. Activation of BMU
2. Initiation of osteoclastic activity
3. Resorption forms small cavity
4. Osteoblast maturation/recruitment
5. Osteoid formation
6. Maturation of osteoid
27
What does RANK-L do?
Signals pre-osteoclasts to mature into active osteoclasts
28
What does osteoprotogerin do?
Inhibits RANK-L
29
How do estrogen and calcitonin affect bone remodeling?
Inhibit osteoclast activity
30
How does acidosis affect bone remodeling?
Promotes osteoclast resorption
31
What are metabolic disorders of bone?
- Osteoporosis
- Osteomalacia
- Paget's disease
32
Name the osteochondroses
- Osteonecrosis (avascular)
| - Apophysitis (epiphysitis)
33
Osteopenia
- Low bone mineral density (BMD)
| - Between 1 and 2.5 SD below the young adult mean
34
Osteoporosis
- Severe decrease in BMD
- 2.5 SD or more below young adult mean
- Osteoclast activity is greater than osteoblast activity
35
Osteomalacia
- "Softening" of the bone
| - Insufficient mineralization (no loss of bone)
36
Osteopetrosis
Increased BMD
37
Primary osteoporosis
- Unrelated to any underlying disease
- Type 1 (postmenopausal, cancellous bone)
- Type 2 (age related, both cortical and cancellous bone)
38
Secondary osteoporosis
Secondary to medication or disease
39
3 phases of bone mass
Growth - 90% of bone density is reached here
Consolidation - remaining 10% of bone density gained
Involution - gradual loss of bone
40
When is peak bone mass commonly reached?
By 30 years old
41
Age related rate of bone density loss is greater in males, less in males, or equal between both?
Equal
42
How much bone mass is loss per year due to age?
Approx. 0.5-1% each year
43
Rate of bone loss in women is ___ after menopause
Accelerated (approx. 3-5% per year)
44
Estrogen loss in menopause affects which players in bone remodeling?
- Higher levels of RANK-L (promotes maturation of osteoclasts)
- Reduced levels of OPG (inhibits maturation)
45
Menopause affects which type of bone most significantly?
Cancellous (trabecular)
| *Vertebrae, metaphysis of long bones
46
Which drugs in particular can cause secondary osteoporosis?
- Corticosteroids
| - Immunosuppressants
47
Why is trabecular bone very sensitive to conditions that alter osteoblast/clast activity?
- Larger surface area and not as large mass to begin with compared to cortical bone
- Experiences greater loss
48
How does tobacco increase risk for osteoporosis?
Impairs bone progenitor cells (inhibiting osteoblast activity)
49
How does alcohol increase risk for osteoporosis?
- Impairs osteoblast activity
- Impairs Ca absorption
- Increases renal excretion of Ca
50
What is the female triad?
- Eating disorder
- Amenorrhea
- Osteoporosis
51
A decrease in 1 SD of BMD will increase risk of fracture by:
1.5 to 3x
52
What is the gold standard for diagnosing osteoporosis?
DEXA
53
Why is x-ray a poor screening tool for osteoporosis?
It only detects bone loss after significant loss has occurred
54
What is Rickets?
Childhood osteomalacia
55
What type of fractures are seen with osteomalacia?
"Looser's zones" or milkman's pseudofractures
56
Describe Paget's disease and epidemiology
- Disease that results in bone deformation
- Excessive resorption is followed by excessive bone formation
- Onset 50+ yo
- Males more than females
57
Describe osteonecrosis (avascular necrosis)
- Death of bone due to loss of blood supply
- Often no symptoms
- Femoral head is MC site
58
What is apophysitis and what are common examples?
- A traction apophysitis of the secondary ossification center
- Osgood-Schlatter disease (patella tendon pulling on tibial tuberosity)
- Olecranon (throwing athletes)
- Sever's disease (Achille's)
59
What is osteomyelitis?
Inflammation of bone caused by bacteria or other infectious agents
60
What is exogenous osteomyelitis?
Trauma exposes bone to bacteria and other foreign material
61
What is endogenous osteomyelitis?
Infection spreads to bone from pre-existing systemic infection (S. aureus is common)
62
How does osteomyelitis occur?
- The physical arrangement of bone contains regions that immune defense mechanisms are unable to access
- This makes bones susceptible to infection if bacteria gains access
63
How does osteomyelitis form in children?
Sequestrum (piece of dead bone) and involucrum (layer of new bone) formation
64
How does bone respond to a primary benign tumor?
Forms a sclerotic rim in order to contain the tumor
| *These do NOT tend to cause pain like malignant tumors
65
Bone tumor descriptions on imaging
- Geographic (well defined margins)
- Moth eaten (less defined margins)
- Permeative (poor margins)
