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Rheum Boards Studying > Bone > Flashcards

Bone Flashcards

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
Q

Factors affecting bone synthesis

A
  • Calcium intake
  • Latitude
  • Exposure to sunlight
  • Ingestion of vitamin D
  • Metabolic state
  • Nutritional status
  • Hormones
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26
Q

Peak bone mass

A
  • Level of bone mass achieved at the end of skeletal maturation
  • Usually reached in late adolescence during second decade
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27
Q

Intrinsic factors that effect bone mass

A
  • Hereditary (Race, genes for vitamin D receptors, IL-6, calcitonin, TGF B, estrogen receptor A, osteocalcin etc)
  • Sex
  • Hormones
28
Q

Extrinsic factors that affect skeletal bone mass

A
  • Calcium

- General state of health

29
Q

How do steroids impact calcium?

A
  • Decrease GI calcium absorption and increase urinary excretion
30
Q

What are the benefits of weight bearing?

A
  • Enhance bone mineral accrual in children, esp in early puberty
31
Q

Dual energy XR absorptiometry (DEXA)

A
  • 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
Q

Quantitative computerized tomography

A
  • Axial skeleton only

- True volumetric density can be measured

33
Q

Tendons

A
  • Major component is Type I collagen

- Attach muscle to bone

34
Q

Ligament

A
  • Function is to joint bone to bone, stabilize the joint, limit mobility
35
Q

Entheses

A
  • Attach tendon, ligament, fascia or capsule to bone
36
Q

Two types of entheses

A
  • Fibrous

- Fibrocartilaginous

37
Q

Fibrous

A
  • Found at attachment of tendon to metaphysis or diaphysis composed of dense fibrous tissue, probably not important in rheum
38
Q

Fibrocartilaginous

A
  • Present on epiphyses of long bones and small bones of hands and feet
  • Achilles, knee, foot
39
Q

Muscle bundle (Fascicle)

A
  • Group of muscle fibers ensheathed by a perimysium
40
Q

What is the basic unit of muscle?

A

Fiber–> made of myofibrils

41
Q

What is the basic contractile unit?

A
  • Sarcomere
  • Made of thin (actin) and thick (myosin) myofilaments
  • Gives muscle striated appearance
42
Q

Epimysium

A
  • Surrounds a skeletal muscle
43
Q

Perimysium

A
  • Surrounds individual fascicles
44
Q

Alpha motor neurons

A
  • Cause action potential that stimulates calcium diffusion in the myoplasm and binding to thin-filament regulatory proteins
45
Q

Type I muscle fibers

A
  • Slow/red
  • Narrower
  • Poorly defined myofibrils
  • Irregular in size
  • Thick Z bands
  • Rich in mitochondria and oxidative enzymes
  • Poor in phosphorlyases
  • Sustained contractions
46
Q

Type II muscle fibers

A
  • Fewer mitochondria and poor in oxidative enzymes
  • Rich in phosphorylases and glycogen
  • Acute strength
47
Q

Z band (disk)

A

Helps to define the sarcomere

48
Q

I band

A
  • Surrounds the Z disk

- Zone of thin filaments (actin) not superimposed by thick filaments

49
Q

A band

A
  • Contains the entire length of single thick filament
50
Q

M Line

A

Inside the H zone of thick filaments not superimposed by thin filaments
- Formed by cross connective elements of the cytoskeleton

51
Q

What is the arterial supply of the long bone?

A
  • Arises from nutrient artery that penetrates the diaphysis and terminates in end arteries at epiphyseal plate
52
Q

What is the arterial supply of the epiphyses?

A

Juxta-articular arteries which also supply the synovium

53
Q

When does arterial communication between the metaphyseal and epiphyseal synovial circulations occurs?

A
  • Not until growth has ceased
54
Q

Components of ECM of hyaline cartilage

A

Collagen fibers, water, proteins and proteoglycans

55
Q

3 compartments of ECM matrix of hyaline cartilage

A

Inner rim: Aggrecan rich, surrounds chondrocytes, no crosslinking
Middle rim: Aggrecan bound to hyaluronan
Outer rim: fine collagen fibrils

56
Q

Three major classes of collagen

A
  1. FIbril forming
  2. Non fibril forming
  3. Fibril associated collagens with interrupted triple helices (FACITS)
57
Q

Type I collagen

A

Most connective tissues, bone, skin, tendons

58
Q

Type II collagen

A

Cartilage, intervertebral disk, vitreous humor

59
Q

Type III

A

Most connective tissues, particularly skin, lung, blood vessel

60
Q

What is a proteoglycans?

A

Macromolecules consisting of a protein core with attached GAG

61
Q

Keratan sulfate

A

Serum concentration of this reflects cartilage metabolism

62
Q

Where can you find elastin?

A
  • Walls of blood vessels

- Ligaments

63
Q

What are the properties of elastin

A
  • Lack tensile strength of collagens but can stretch than return to original length
  • Produced by fibroblasts and smooth muscle cells
64
Q

Laminin

A

Major constituent of the basement together with Type IV collagen

65
Q

Fibronectin

A

Dimeric glycoprotein that acts as attachment protein in ECM

Rheum Boards Studying (34 decks)

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