Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
72 Cards in this Set
- Front
- Back
|
How are osteons formed?
|
Remodeling of compact bone (replace old & damaged areas)
|
|
|
How does replacement of trabecular bone usually occur?
|
Absorption pits (can also be by osteons)
|
|
|
What are the functions of trabeculum?
|
1. Orientation allows forces in multiple directions
2. Light weight but strong |
|
|
Osteocytes are connected to other cells by?
|
Cytoplasmic extensions passing through canaliculi
|
|
|
Which layer of the osteon is the oldest layer?
|
Outer layer
|
|
|
What is the major protein found in bone matrix?
|
Type I collagen
|
|
|
How is collagen deposited in bone matrix?
|
Osteoblasts
|
|
|
Fibers of woven bone are laid in what direction?
|
Varying directions
|
|
|
Fibers of laminar bone are laid in which direction?
|
Each layer of fibers are oriented in a different direction
|
|
|
Which proteins are found in bone matrix? (4)
|
1. Collagen
2. Osteocalcin 3. Osteopontin 4. Osteonectin |
|
|
What is osteocalcin?
|
Ca binding protein w/ Gla sequences & is Vitamin K dependent
|
|
|
What types of growth factors are found in bone matrix? (3)
|
1. TGF-beta
2. IGF-1 3. IGF-2 4. BMPs |
|
|
Function of growth factor binding proteins?
|
Store, protect & inhibit/activate growth factor action
|
|
|
What is osteopontin?
|
Binds osteoclasts
RGD sequence Binds Ca & collagen |
|
|
What is osteonectin?
|
Protein that binds Ca & collagen
|
|
|
Hydroxyapatite makes up what percentage of bone content?
|
50%
|
|
|
Function of hydroxyapatite in bone matrix?
|
Supports pressures applied to bone
|
|
|
IGF-1 activates which second messenger pathway?
|
Tyrosine kinase pathway
|
|
|
What is noggin?
|
Inhibitor of BMP pathway
|
|
|
What is heterotrophic ossification?
|
Excessive bone growth following amputation
May occur in spine below spinal injury |
|
|
How does noggin function?
|
Inhibits signaling of BMPs by preventing their interaction w/ receptors on cell surface
|
|
|
Structure of noggin is very similar to?
|
BMP-7
|
|
|
Noggin plays key role in?
|
Formation of nervous system by inhibiting BMP-4
|
|
|
How is noggin crucial in bone development?
|
Regulates function of BMPs
|
|
|
Mutation of noggin gene leads to?
|
Skeletal dysplasias
|
|
|
What cell type has a common precursor w/ osteoclasts?
|
Monocytes
|
|
|
Where are osteoclasts commonly found?
|
1. Endosteal surfaces
2. Haversian canals |
|
|
Where are osteoclasts rarely found?
|
Periosteal surfaces
|
|
|
Nuclei of osteoclasts?
|
Large multinucleated (10-20)
|
|
|
Where is the ruffled border of osteoclasts located?
|
Next to bone surface-- release enzymes & acids
|
|
|
Osteoclasts form what in the bone? (2)
|
1. Reabsorption pits (Howship's lacuna)
2. Tunnels |
|
|
Layers of periosteum?
|
1. Outer layer-- very fibrous
2. Inner layer-- cellular w/ blood vessels, nerves |
|
|
In what type of bones is inner layer more extensive?
|
Growing bones
|
|
|
What happens in the BMP 2nd messenger cascade?
|
BMP binds receptor --> activates Smads (transcription factors) -->Smads activate other TFs and turn on genes
|
|
|
Mutation in Noggin gene that decreases inhibitory effect of noggin on BMP4 causes a disease know as?
|
Fibrodysplasia ossificans progressiva (FOP)-- heterotrophic osteogenesis
|
|
|
What happens in people w/ FOP?
|
Excessive bone is formed (primarily in skeletal muscles)-- Osteblasts are formed by BMP4 acting on mesenchymal cells
|
|
|
New bone formation in FOP appears to follow?
|
Inflammation occurring a specific area of the muscle--> increased action of BMP4 in these areas
|
|
|
How is a tooth bud made? (4)
|
1. Mix epithelial cells & mesenchymal cells in collagen gel
2. Culture for 5-7 days 3. Extract tooth & allow wound heling 4. Transplant bio-engineered tooth |
|
|
Most arteries in bone originate from?
|
Nutrient arteries distributed along endostem
|
|
|
Where are capillaries located in bone?
|
2 in each erosion canal
|
|
|
Most veins exit where in bone?
|
Periosteum
|
|
|
What is the osteoblast lineage? (5)
|
1. Mesenchymal stem cell
2. Early pre-osteoblast 3. Late pre-osteoblast 4. Mature osteoblast or bone lining cell 5. Osteocyte or death by apoptosis |
|
|
What stimulates differentiation of mesenchymal cell to early pre-osteoblast?
|
BMPs
|
|
|
What stimulates proliferation & differentiation of early pre-osteoblast to late pre-osteoblast? (2)
|
1. BMPs
2. IGF-1,2 |
|
|
What stimulates late pre-osteoblast to develop into mature osteoblast or bone lining cell?
|
IGF-1,2
|
|
|
Osteoblasts have what on outside surface of cells & that are important for what?
|
Alkaline phosphatase-- important in mineralization
|
|
|
What are the only cell type found within bone matrix?
|
Osteocytes
|
|
|
Osteocytes cell processes extending in canaliculi are connected to other processes & cells on bone surface by?
|
Gap junctions
|
|
|
What do both mature osteoblasts & osteocytes have in common?
|
Do not multiply
|
|
|
What are the functions of osteocytes? (3)
|
1. Help maintain bone
2. Sense application of periodic pressure 3. Transport Ca through canaliculi into circulation (osteocytic osteolysis) |
|
|
What is a quick way to increase ECF Ca?
|
Osteocytic osteolysis
|
|
|
What surrounds ruffled border of osteoclasts?
|
Clear zone (free of organelles)
|
|
|
How does clear zone attach to bone?
|
Intercellular actin filaments in clear zone of cytoskeleton of osteoclasts are attached to integrins which are attached to extracellular collagen by attachment proteins
|
|
|
What types of attachment proteins attach integrins to collagen?
|
Proteins w/ RGD sequence (fibronectin or vitronectin)
|
|
|
What releases osteoclasts from extracellular matrix?
|
Phosphorylation of integrin receptor by kinase
|
|
|
Activators of osteoclasts? (3)
|
1. PTH
2. 1,25 D3 3. ODF (RANK-L) |
|
|
Inhibitors of osteoclasts? (2)
|
1. Calcitonin
2. OPG (osteoprotegrin) |
|
|
Steps of osteoclast differentiation? (5)
|
1. Bone marrow stem cell
2. Pre-monocyte/osteoclast 3. Early pre-osteoclast 4. Late pre-osteoclast 5. Osteoclast |
|
|
What promotes fusion of pre-osteoclasts?
|
PTH & 1,25 D3
|
|
|
ODF is produced by?
|
pre-osteoclasts
|
|
|
What is ODF?
|
Juxtacrine factor attached to outside of pre-osteoclasts
|
|
|
ODG (osteoprotegrin) is produced by?
|
Osteoblast lineage cell
|
|
|
What happens when ODG binds ODF?
|
Blocks action of ODF & inhibits osteoclast formation
|
|
|
How is bone resorbed by osteoclasts? (3)
|
1. Osteoclasts form resorption pits (Howship's lacuna)
2. H+ dissolve bone mineral & provide proper pH for enzymes 3. Enzymes degrade ECM |
|
|
How is compact bone remodeled? (3)
|
1. Erosion canal formed by osteoclasts
2. Osteoblasts fill canal w/ new bone 3. New osteon formed w/ in compact bone |
|
|
How are H+ ions secreted into area of bone resorption?
|
Primary active transporters (w/ Cl) in membrane of ruffled border
|
|
|
Which class of primary active transporters are found on osteoclast's plasma membrane?
|
V-class
|
|
|
What is bone coupling & what stimulates it?
|
During bone remodeling, the bone removed is replaced by the same amount of bone-- release of growth factors that were bound to proteins stimulate replacement
|
|
|
What is osteopetrosis & what causes it?
|
Very dense bone -- when osteoclasts don't function
|
|
|
Deficiency in carbonic anhydrase II causes? (2)
|
1. Osteopetrosis
2. Renal tubular acidosis |
|
|
Usual causes of bone loss? (3)
|
1. Aging
2. Decreased estrogen & testosterone 3. Lack of exercise |
|
|
Increased bone loss due to increased? (6)
|
1. Glucocorticoids
2. Thryoxine 3. Alcoholism 4. Removal of part or all of stomach or GI diseases 5. Hypercalciuria 6. Smoking |
