Alveolar bone formation and resorption Flashcards
what makes up the alveolar bone proper
cribriform plate or bundle bone
what is the cribriform plate formed as a result of
attachment of the PDL fibers and passage of vessels and nerves into and out of the PDL
what does the term bundle bone refers to
bone in which sharpeys fibers are embedded
what is woven bone
immature/newly formed bone in which the collagen fiber matrix is randomly oriented
-newly formed bone
describe woven bone in comparison to mature bone
-has more cells per unit area
-contains a greater volume of non-collagenous protein
-forms more rapidly than mature bone
what is lamellar bone
mature/secondarily formed bone. can be classified as spongy/cancellous and compact/cortical
what is spongiosa/cancellous bone
trabecular bone that lies between the cortical plates and within the marrow spaces
describe cancellous bone
-trabeculae lined with osteoblasts
-random orientation of collagen fibers
- facial and lingual cortical plates: made of lamellar bone, haversian bone, or interstitial bone
what is the compostion of bone
-67% inorganic (calcium hydroxyapatite)
- 33% organic (28% collagen and 5% proteins (osteocalcin, sialoprotein, osteonectin, BMP) )
what is osteoid
bone matrix formed by osteoblasts (5-10 um increments)
what do osteoblasts do
make bone
what do osteoclasts do
remove bone
what do osteocytes do
osteoblasts that have been entrapped by its own osteoid matrix
what do bone lining cells do
flattened inactive osteoblasts that line trabecular bone. protect bony surface from osteoclast activity
what do chondroblasts do
lay down cartilage
what do condrocytes do
remove cartilage
what do mesenchymal cells do
undifferentiated cells
what do canaliculi do
allow osteoblasts and osteoclasts to communicate with outside environment
-mechanoreception properties
where do canaliculi radiate
all directions
-processes of the osteocytes travel within the canaliculi and connect to other osteocytes/osteoblasts allowing cell to cell communication
what is the periosteum
a dense connective tissue bound to bone by sharpeys fibers that contain blood vessels, nerves and three cell layers
what are the 3 cell layers in the periosteum and what makes up each
-peripheral cell layer of fibroblasts
- intermediate cell layer of undifferentiated mesenchymal cells
-proximal layer of osteoblasts
what is the endosteum
lines the medullary cavity and cancellous bone
-same composition as periosteum but significantly thinner
what are the collagen proteins associated with bone and where are they located
- 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
what are the non-collagenous proteins associated with bone
osteonectin, osteopontin, osteocalcin, BMP and others
what are non collagenous proteins characterized by
-highly acidic nature
-high aggregation tendencies
- calcium binding properties
what does bone formation consist of
- in-situ remodeling
- intramembranous bone formation
- endochondral bone formation
what is in-situ remodeling
osteoclastic resorption and bone replacement by osteoblast activity
where is in situ remodeling seen
in alveolar bone affected by orthodontics
what happens in intramembranous bone formation
-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
what do matrix vesicles in intramembranous bone formation contain
pryophosphate, alkaline phosphatase, glycoproteins, phosphoproteins, phospholipids
what does alkaline phosphatase do
helps mineralize collagen
what is endochondral bone formation
-bone formation within hyaline cartilage that involves a concomitant replacement of the cartilage framework by bone
where is endochondral bone formation found
in vertebrae, long bones, base of the skull, and head of mandible
what is the process of endochondral bone formation
-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
what is endochondral growth of bones dependent on
the growth of the cartilage and stops once the cartilage has been completely removed
what are the zones of cellular activity and what happens in each
-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
what is bone metabolism controlled by locally and systemically
systemically by hormones and locally by mechanical factors, growth factors, and cytokines
how are hormones important to bone metabolism and which hormones
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
what do cytokines and growth factors do and which are involved
cause osteoblasts to stimulate formation of osteoclasts and indirectly cause bone resorption
-IL-1,IL-6,BMP-2, BMP-7, TRF, IGF, FGF, PDGF
what does IL6 do
promote differentation of osteoblasts
how does osteoclastic resorption work
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
what is the resorption reaction
CO2 + H2O -> HCO3- + H+
describe the resorption reaction
-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
