Alveolar bone formation and resorption

Question 1

what makes up the alveolar bone proper

Answer 1

cribriform plate or bundle bone

Question 2

what is the cribriform plate formed as a result of

Answer 2

attachment of the PDL fibers and passage of vessels and nerves into and out of the PDL

Question 3

what does the term bundle bone refers to

Answer 3

bone in which sharpeys fibers are embedded

Question 4

what is woven bone

Answer 4

immature/newly formed bone in which the collagen fiber matrix is randomly oriented
-newly formed bone

Question 5

describe woven bone in comparison to mature bone

Answer 5

-has more cells per unit area
-contains a greater volume of non-collagenous protein
-forms more rapidly than mature bone

Question 6

what is lamellar bone

Answer 6

mature/secondarily formed bone. can be classified as spongy/cancellous and compact/cortical

Question 7

what is spongiosa/cancellous bone

Answer 7

trabecular bone that lies between the cortical plates and within the marrow spaces

Question 8

describe cancellous bone

Answer 8

-trabeculae lined with osteoblasts
-random orientation of collagen fibers
- facial and lingual cortical plates: made of lamellar bone, haversian bone, or interstitial bone

Question 9

what is the compostion of bone

Answer 9

-67% inorganic (calcium hydroxyapatite)
- 33% organic (28% collagen and 5% proteins (osteocalcin, sialoprotein, osteonectin, BMP) )

Question 10

what is osteoid

Answer 10

bone matrix formed by osteoblasts (5-10 um increments)

Question 11

what do osteoblasts do

Answer 11

make bone

Question 12

what do osteoclasts do

Answer 12

remove bone

Question 13

what do osteocytes do

Answer 13

osteoblasts that have been entrapped by its own osteoid matrix

Question 14

what do bone lining cells do

Answer 14

flattened inactive osteoblasts that line trabecular bone. protect bony surface from osteoclast activity

Question 15

what do chondroblasts do

Answer 15

lay down cartilage

Question 16

what do condrocytes do

Answer 16

remove cartilage

Question 17

what do mesenchymal cells do

Answer 17

undifferentiated cells

Question 18

what do canaliculi do

Answer 18

allow osteoblasts and osteoclasts to communicate with outside environment
-mechanoreception properties

Question 19

where do canaliculi radiate

Answer 19

all directions
-processes of the osteocytes travel within the canaliculi and connect to other osteocytes/osteoblasts allowing cell to cell communication

Question 20

what is the periosteum

Answer 20

a dense connective tissue bound to bone by sharpeys fibers that contain blood vessels, nerves and three cell layers

Question 21

what are the 3 cell layers in the periosteum and what makes up each

Answer 21

-peripheral cell layer of fibroblasts
- intermediate cell layer of undifferentiated mesenchymal cells
-proximal layer of osteoblasts

Question 22

what is the endosteum

Answer 22

lines the medullary cavity and cancellous bone
-same composition as periosteum but significantly thinner

Question 23

what are the collagen proteins associated with bone and where are they located

Answer 23

• type 1: fibrillar, located everywhere
• type 2: fibrillar: primarily a cartilage protein found in endochondral bone formation
  -type 3: fibrillar, granulation and mesenchymal tissues found in healing tissues
• type 5:fibrillar, stromal connective tissues. promotes cellular attachment and migration
  type 10: growth plate, facilitates conversion of cartilage -> bone

Question 24

what are the non-collagenous proteins associated with bone

Answer 24

osteonectin, osteopontin, osteocalcin, BMP and others

Question 25

what are non collagenous proteins characterized by

Answer 25

-highly acidic nature -high aggregation tendencies - calcium binding properties

Question 26

what does bone formation consist of

Answer 26

1. in-situ remodeling 2. intramembranous bone formation 3. endochondral bone formation

Question 27

what is in-situ remodeling

Answer 27

osteoclastic resorption and bone replacement by osteoblast activity

Question 28

where is in situ remodeling seen

Answer 28

in alveolar bone affected by orthodontics

Question 29

what happens in intramembranous bone formation

Answer 29

-bone formation within or between CT membranes consisting of type 1 collagen -found in the inner spongy layers of bone -extremely rapid and disorganized method of bone deposition -osteoblasts secrete matrix vesicles that mineralize surrounding collagen fibers. the osteoblasts become trapped and become osteocytes

Question 30

what do matrix vesicles in intramembranous bone formation contain

Answer 30

pryophosphate, alkaline phosphatase, glycoproteins, phosphoproteins, phospholipids

Question 31

what does alkaline phosphatase do

Answer 31

helps mineralize collagen

Question 32

what is endochondral bone formation

Answer 32

-bone formation within hyaline cartilage that involves a concomitant replacement of the cartilage framework by bone

Question 33

where is endochondral bone formation found

Answer 33

in vertebrae, long bones, base of the skull, and head of mandible

Question 34

what is the process of endochondral bone formation

Answer 34

-mesenchymal cells create a general outline/shape of what the final bone will look like - cells differentiate into chondroblasts which increase in size, secrete collagen and mineralize it with matrix vesicles -vascular tissue from surrounding perichondrium invades cartilage, allowing chondrocytes chondroclasts and mesenchymal cells to enter the area - chondroclasts eat away the cartilage and newly differentiates osteoblasts deposit osteoid into the cartilage - osteoid is mineralized by osteocytes and bone is made

Question 35

what is endochondral growth of bones dependent on

Answer 35

the growth of the cartilage and stops once the cartilage has been completely removed

Question 36

what are the zones of cellular activity and what happens in each

Answer 36

-reserve or resting chondrocytes: hyaline cartilage rests - proliferation: collagen starts to form - maturation: less division of cells but chondrocytes are increasing in size - hypertrophy and calcification: where areas become evaluated -cartilage degeneration: chondrocytes die - osteogenesis: osteoblasts come in with capillaries. osteoblasts differentiate and bone formation occurs

Question 37

what is bone metabolism controlled by locally and systemically

Answer 37

systemically by hormones and locally by mechanical factors, growth factors, and cytokines

Question 38

how are hormones important to bone metabolism and which hormones

Answer 38

affect absorption both directly and indirectly, can cause absoprtion or formation depending on concentration and interactions with each other - PTH, Vit D3, calcitonin, estrogen and glucocorticoids

Question 39

what do cytokines and growth factors do and which are involved

Answer 39

cause osteoblasts to stimulate formation of osteoclasts and indirectly cause bone resorption -IL-1,IL-6,BMP-2, BMP-7, TRF, IGF, FGF, PDGF

Question 40

what does IL6 do

Answer 40

promote differentation of osteoblasts

Question 41

how does osteoclastic resorption work

Answer 41

decreases pH to demineralize hydroxyapatite and enzymes such as lactic acid, citric acid, H+, acid phosphatase, aryl sulfatase, collagenase, and gelatinase degrade the bone matrix

Question 42

what is the resorption reaction

Answer 42

CO2 + H2O -> HCO3- + H+

Question 43

describe the resorption reaction

Answer 43

-carbon dioxide and water are catalyzed by carbonic anhydrase resulting in bicarbonate and free protons - bicarbonate gets removed and free protons are there to help demineralize and break down the bone