Rheum Boards Studying > Bone > Flashcards

Bone Flashcards

(65 cards)

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1
Q

Cortical bone

A
  • Forms the external surface
  • Prominent in tubular long bone
  • Provides strength
  • Made of tightly packed osteons (Haversian systems)
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2
Q

Trabecular bone

A
  • Lies beneath the cortex
  • Predominates in vertebral bodies, flat bones of the pelvis and skull
  • Much less organized than cortical bone
  • Consisting of interconnecting trabeculae, larger blood vessels and bone marrow
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3
Q

Epiphysis

A
  • Separated from the metaphysis by the physis (growth plate)
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4
Q

Diaphysis

A
  • Joins the two metaphysis and provides length
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5
Q

Apophyses

A
  • AKA tibial tuberosity are the site of new bone formation like the epiphyses but do not contribute to bone length
  • They lay down new bone in response to traction
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6
Q

Periosteum

A
  • Covers bone except for articular surfaces
  • Fibrous outer layer is site of attachment of muscles
  • Inner layer contains osteoblasts that generate new bone
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7
Q

Where does linear growth occur?

A

Physis

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8
Q

Where does circumferential growth occur?

A

Periosteal deposition

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9
Q

When does the growth of the appendicular skeleton cease?

A

Ossification of the iliac apophyses

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10
Q

When does the height of the vertebral bodies cease?

A

Until the 3rd decade

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11
Q

How can skeletal bone age be determined?

A
  • Can be determined by secondary ossification and physeal closure (earlier in girls)
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12
Q

What factors influence growth at the physis?

A
  • Thyroxine
  • GH
  • IGF-1
    (these three work together to cause peak bone mass during puberty)
  • Testosterone (anabolic effect)
  • Estrogens suppress the growth rate by increasing the calcification of the matrix (prerequisite to epiphyseal closure)
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13
Q

Biochemical composition of bone

A
  • 70% minerals and 30% organic constituents
  • Hydroxyapatite (mostly Ca and Phos) accounts for 95% of minerals with Mag
  • Organic component is 98% matrix, mostly type I collagen and non collagenous protein ( osteocalcin, fibronectin, osteonectin, and osteopontin)
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14
Q

What makes up the other 2% of the organic component?

A

Bone cells

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15
Q

What do bone cells do?

A
  • Responsible for formation, resorption and maintenance of the remodeling cycle
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16
Q

Osteoclasts

A
  • Derived from mononuclear cells and resorb bone
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17
Q

Osteoblasts

A
  • Form osteoid and osteoid matrix
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18
Q

Osteocytes

A
  • Differentiated osteoblasts and maintain the integrity of bone through a network of canaliculi
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19
Q

Alkaline Phosphatase

A
  • Enzyme secreted by osteoblasts, but also other cells (liver, gut, kidneys)
  • In children, 50 percent from bone
  • Released during osteoblastic activity
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20
Q

Osteocalcin

A
  • Synthesized by osteoblasts and chondrocytes and deposited in extracelullar bone matrix
  • Sensitive and specific marker of bone formation
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21
Q

Acid phosphatase (TRAP)

A
  • Present in osteoclast and released during osteoclastic activity
  • Not bone specific
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22
Q

Urinary calcium to Cr ratio

A
  • Marker of bone resorption

- Elevated values indicate hypercalcemia and increased bone resorption

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23
Q

What is the role of parathyroid hormone?

A
  • Maintains Ca concentration in the blood
  • Stimulates osteoclastic activity causing bone resorption (and increased serum calcium)
  • Stimulates conversion 25 (OH)D3 to 1, 25 (OH)2D3
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24
Q

Calcitriol

A
  • Stimulates intestinal absorption of calcium, elevating serum calcium concentration
  • Receptors present on intestinal cells
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25
Factors affecting bone synthesis
- Calcium intake - Latitude - Exposure to sunlight - Ingestion of vitamin D - Metabolic state - Nutritional status - Hormones
26
Peak bone mass
- Level of bone mass achieved at the end of skeletal maturation - Usually reached in late adolescence during second decade
27
Intrinsic factors that effect bone mass
- Hereditary (Race, genes for vitamin D receptors, IL-6, calcitonin, TGF B, estrogen receptor A, osteocalcin etc) - Sex - Hormones
28
Extrinsic factors that affect skeletal bone mass
- Calcium | - General state of health
29
How do steroids impact calcium?
- Decrease GI calcium absorption and increase urinary excretion
30
What are the benefits of weight bearing?
- Enhance bone mineral accrual in children, esp in early puberty
31
Dual energy XR absorptiometry (DEXA)
- Gold standard - Low radiation, high speed and accuracy - Gives areal BMD (not true volumetric density) - Should be interpreted with age matched controls and corrections for height, weight and geography
32
Quantitative computerized tomography
- Axial skeleton only | - True volumetric density can be measured
33
Tendons
- Major component is Type I collagen | - Attach muscle to bone
34
Ligament
- Function is to joint bone to bone, stabilize the joint, limit mobility
35
Entheses
- Attach tendon, ligament, fascia or capsule to bone
36
Two types of entheses
- Fibrous | - Fibrocartilaginous
37
Fibrous
- Found at attachment of tendon to metaphysis or diaphysis composed of dense fibrous tissue, probably not important in rheum
38
Fibrocartilaginous
- Present on epiphyses of long bones and small bones of hands and feet - Achilles, knee, foot
39
Muscle bundle (Fascicle)
- Group of muscle fibers ensheathed by a perimysium
40
What is the basic unit of muscle?
Fiber--> made of myofibrils
41
What is the basic contractile unit?
- Sarcomere - Made of thin (actin) and thick (myosin) myofilaments - Gives muscle striated appearance
42
Epimysium
- Surrounds a skeletal muscle
43
Perimysium
- Surrounds individual fascicles
44
Alpha motor neurons
- Cause action potential that stimulates calcium diffusion in the myoplasm and binding to thin-filament regulatory proteins
45
Type I muscle fibers
- Slow/red - Narrower - Poorly defined myofibrils - Irregular in size - Thick Z bands - Rich in mitochondria and oxidative enzymes - Poor in phosphorlyases - Sustained contractions
46
Type II muscle fibers
- Fewer mitochondria and poor in oxidative enzymes - Rich in phosphorylases and glycogen - Acute strength
47
Z band (disk)
Helps to define the sarcomere
48
I band
- Surrounds the Z disk | - Zone of thin filaments (actin) not superimposed by thick filaments
49
A band
- Contains the entire length of single thick filament
50
M Line
Inside the H zone of thick filaments not superimposed by thin filaments - Formed by cross connective elements of the cytoskeleton
51
What is the arterial supply of the long bone?
- Arises from nutrient artery that penetrates the diaphysis and terminates in end arteries at epiphyseal plate
52
What is the arterial supply of the epiphyses?
Juxta-articular arteries which also supply the synovium
53
When does arterial communication between the metaphyseal and epiphyseal synovial circulations occurs?
- Not until growth has ceased
54
Components of ECM of hyaline cartilage
Collagen fibers, water, proteins and proteoglycans
55
3 compartments of ECM matrix of hyaline cartilage
Inner rim: Aggrecan rich, surrounds chondrocytes, no crosslinking Middle rim: Aggrecan bound to hyaluronan Outer rim: fine collagen fibrils
56
Three major classes of collagen
1. FIbril forming 2. Non fibril forming 3. Fibril associated collagens with interrupted triple helices (FACITS)
57
Type I collagen
Most connective tissues, bone, skin, tendons
58
Type II collagen
Cartilage, intervertebral disk, vitreous humor
59
Type III
Most connective tissues, particularly skin, lung, blood vessel
60
What is a proteoglycans?
Macromolecules consisting of a protein core with attached GAG
61
Keratan sulfate
Serum concentration of this reflects cartilage metabolism
62
Where can you find elastin?
- Walls of blood vessels | - Ligaments
63
What are the properties of elastin
- Lack tensile strength of collagens but can stretch than return to original length - Produced by fibroblasts and smooth muscle cells
64
Laminin
Major constituent of the basement together with Type IV collagen
65
Fibronectin
Dimeric glycoprotein that acts as attachment protein in ECM
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