Bone And Skeleton

Front 1

What are the characteristics of cortical bone?

Back 1

1. Fairly stable

2. Lowest turnover

3. Shafts of long bones, surfaces of flat bones

Front 2

What are the characteristics of cancellous bone?

Back 2

1. Less stable

2. High turnover

3. Rapidly exchangeable Ca pool

4. Ends of long bones, vertebrae, internal portion of flat bones

Front 3

What is the main type of collagen in bones?

Back 3

1. Type I

Front 4

What role do proteoglycans play in calcification?

Back 4

1. Have a high ion-binding capacity

Front 5

What is the collagen orientation in lamellar bone?

Back 5

1. Alternate layer to layer

2. Can be parallel (trabecular) or concentric (compact)

3. Structurally superior

Front 6

What is the collagen orientation in woven bone?

Back 6

1. Collagen fibers less organized

2. Forms during rapid turnover

3. Structurally inferior

Front 7

How is hydroxyapatite arranged in bone?

Back 7

1. Arranged in spindles or plate along the collagen fibers and proteoglycan

Front 8

What is required for activation of bone modeling?

Back 8

1. Interaction between osteoclast progenitors and osteoblasts/stromal cells

Front 9

What can act as triggers for activation of bone modeling?

Back 9

1. M-CSF

2. RANK-L

Front 10

What effect does M-CSF have on osteoclast precursor cells?

Back 10

1. Proliferate

2. Express RANK--- activator of RANK-L

Front 11

How does RANK-L participate in activation?

Back 11

1. RANK-L bound to osteoblast cell membrane

2. Osteoclast precursor binds to ligand, begins to express markers unique to osteoclasts

Front 12

How is proto-oncogene c-src activated? What subsequently happens?

Back 12

1. Activated by continued exposure to RANK-L and IL-1

2. Ruffled border subsequently formed

Front 13

What happens in bone resorption?

Back 13

1. Activated osteoclasts bind to osteoid

2. Ruffled border adjacent to bone

Front 14

What is in charge of osteoclast placement and binding at ruffled border?

Back 14

1. integrins

Front 15

What do villi secrete at the ruffled border?

Back 15

1. Proteolytic enzymes

2. Acids

Front 16

What is OPG?

Back 16

1. Decoy receptor secreted by osteoblasts

2. Binds RANK-L and prevents osteoclast activation

Front 17

What is the effect of estrogen on bone modeling?

Back 17

1. Inhibits osteoclastogenesis

2. Exhibits direct effect on bone cells

Front 18

What is direct deactivation?

Back 18

1. Activated osteoclast can be stimulated to de-differentiate

2. Bone resorbing activity can be reduce in active osteoclast

Front 19

What is the effect of calcitonin on osteoclasts?

Back 19

1. Causes osteoclast to shrink and decrease resorption of bone

Front 20

What leads to osteoclast apoptosis?

Back 20

1. Activation of gene locus bcl-2

Front 21

What are the stimulator of stem cell proliferation?

Back 21

1. GH

2. Bone morphogenic proteins (BMPs)

Front 22

What are the stimulators of stromal cell replication/differentiation?

Back 22

1. GH

2. TGF B

3. FGF

4. PDGF

Front 23

What are the stimulators of osteoprogenitor cell replication and differentiation?

Back 23

1. IGF-1, 2

2. PTH

3. PTHrP

4. Glucocorticoids

Front 24

What can act as surrogates for Ca in bone formation? What is a possible side effect?

Back 24

1. Any ion with proper electronic configuration can be incorporated

2. Radioactivity can result if exposure is long enough

Front 25

What happens during osteoblast maturation?

Back 25

1. Osteoblasts mature into osteocytes or lining cells

Front 26

What happens in direct deactivation of osteoblasts?

Back 26

1. PTH and other calcitropic hormones decreases osteoblast activity

Front 27

What leads to osteoblast apoptosis?

Back 27

1. Activation of gene locus bad

Front 28

What is the marker for total bone turnover?

Back 28

1. Osteocalcin

Front 29

What is the marker for bone formation?

Back 29

1. BSAP

Front 30

What is the urine marker for bone resorption?

Back 30

1. Hydroxyproline

Front 31

What is the serum marker for bone resorption?

Back 31

1. TRAP

Front 32

What can determine bone deposition?

Back 32

1. Age

2. Compressional load

Front 33

What is the effect of PTH on bone turnover?

Back 33

1. Promotes RANKL expression on osteoblasts, stimulating osteoclast activation

2. Promotes format of active vitamin D

Front 34

What is the effect of 125-OH-D in bone turnover?

Back 34

1. Promotes maturation of osteoclast progenitor cells

2. Promotes expression of RANKL on osteoblasts, stimulating osteoclast activation

Front 35

What is the effect of GH on bone turnover?

Back 35

1. Induces clonal expansion of osteoblast-type cells

2. Induces osteoblasts to produce IGF

3. Promotes hydroxylation of vitamin D to active form

Front 36

What is the role of IGF in bone turnover?

Back 36

1. Promotes proliferation of osteoblast-type cells

2. Promotes growth of cells

Front 37

What is the role of thyroid hormone in bone turnover?

Back 37

1. Induces activation of new remodeling cycles

2. Number of cycles directly proportional to amount of T3 available

Front 38

What is the role of glucocorticoids in bone turnover?

Back 38

1. Inhibit osteoblast formation/activity

2. Inhibit Ca absorption from the gut

Front 39

What is the effect of gonadotropin on bone turnover?

Back 39

1. Suppress production of osteoclast-inducing cytokines

Front 40

What is the effect of IL-1 and IL-6 on osteoclasts?

Back 40

1. IL-1-- Stimulates all phases of osteoclast production and activation

2. IL-2-- Stimulates osteoclast production

Front 41

What happens in osteopetrosis?

Back 41

1. Net increase in bone due to osteoclast hypofunction

2. Bone shows 'banding' on X-ray

Front 42

What happens in Paget's disease?

Back 42

1. Abnormally high rate of remodeling

2. Net increase in skeletal mass over time

Front 43

What occurs in the osteoclastic phase of Paget's disease?

Back 43

1. Intense resorption of existing bone

Front 44

What occurs in the mixed phase of Paget's disease?

Back 44

1. Intense, disorganized deposition of lamellar bone coincides with continuing osteoclastic activity

Front 45

What occurs in the osteoblastic phase of Paget's disease?

Back 45

1. Formation is dominant

2. Trabeculae are irregular shaped

3. Osteons overlap

Front 46

What occurs in aging-induced osteoporosis?

Back 46

1. Increased osteoclast activity

2. Decreased replication of osteoprogenitor cells

3. Decreased synthesis of matrix proteins by osteoblasts

4. Degradation of biologically active matrix proteins

Front 47

What occurs in secondary osteoporosis?

Back 47

1. Bone degradation due to connective tissue disease, immobilization, or endocrine disorders

Front 48

What endocrine disorders can lead to secondary osteoporosis?

Back 48

1. Hypogonadism-- increased IL-1 and 6

2. Hypercortisolism-- high levels inhibit Ca absorption

3. Hyperthyroidism-- increased number of ARF cycles=poor bone

4. Hyeprparathyroidism-- shift toward osteoclast activity

Front 49

How can cancer influence bone turnover?

Back 49

1. Overproduction of PTHrP

Front 50

What causes vitamin D-dependent osteomalacia?

Back 50

1. Low Ca intake

2. Low skin synthesis of vitamin D

3. Intestinal malabsorption of vitamin D

4. Impaired hydroxylation

Front 51

What causes hypophosphatemia?

Back 51

1. Defects in transporter

2. Paraneoplastic syndrome-- PTHrP

3. Prolonged use of high doses of aluminum-containing antacids

Front 52

What is osteogensis imperfecta?

Back 52

1. Results from mutations in type I collagen a chain

2. Leads to skeletal fragility