Bone Metabolism Flashcards
osteoblast
type of bone cell
synthetic cells and produce bone matrix proteins like type 1 collagen, alkaline phosphatase, osteopontin and osteocalcin
osteocytes are entrapped within matrix after mature from osteoblasts
bone matrix proteins produced by osteoblasts
type 1 collagen
alkaline phosphatase
osteopontin and osteocalcin
osteoclasts
degradative cell- resporoption
multinucleated, ruffled border, tartrate- reistant acid phosphatase (TRAP), cathepsin K
origin of osteoclasts vs osteoblasts
osteoclacsts are hematopoietic origin as opposed to osteoblasts
what type of bone is seen in the skull more
more compact bone than spongy bone
T/F a lot of blood supply in the compact bone (located more on the outside)
TRUE
feature of spongy bone
gives maximum strength with minimum amount of weight
structures located in the central canal system of bones
artery with capillaries, vein, and nerve fiber
bulk of fibers in osteon are?
collagen fibers - which provides the maximum strength
the collagen fiber structure will dictate how large the crystals of mineral will be in the skeleton
T/F the blood vessels continue into the medullary cavity containing the marrow
TRUE
endosteum
layer of bone lining the bony canals and covering the trabeculae
synonyms for spongy bone
cancellous bone and trabeculae bone and diploe
where will you find an ossification center?
appears in the fibrous connective tissue membrane
describe an ossificatoin center in the fibrous connective tissue membrane
selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center
after an ossification center is seen/produced?
osteoblasts begin to secrete OSTEOID - which is the bone matrix and this is secreted within the fibrous membrane
where is the osteoid secretes?
WITHIN the fibrous membrane - the osteoblasts become osteocytes
when is the matrix mineralized once secreted?
within a few days
3rd step in bone formation
woven bone and periosteum form
4th step in bone formation
bone collar of compact bone forms and red marrow appears
describe what happens with woven bone and periosteum formation
accuulating osteoid is laid down BETWEEN EMBRYIONIC BLOOD VESSELS, which form a random network which is termed network of trabeculae NOT lamellae
vascularized mesenchyme condenses on the external face of the woven bone and become the periosteum
what forms the periosteum
condensing mesenchyme
describe the bone collar of compact bone forms and how red marrow appears (4th step)
trabeculae just deep to the periosteum thickening, forming a woven bone collar that is later replaced with mature lamellar bone
the spongy bone consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow
another name for compact bone
lamellar bone
what becomes the red marrow
vascular tissue within the spongy bone/trabeculae
what forms the bone collar
thickening just beneath to the periosteum - later this is replaced with mature lamellar bone
what do the diploe cavities contain?
diploe (aka spongy bone) cavities contains red marrow
pre cursor of long bone formation
cartilage
what has to happen with a cartilage precursor bone formation?
chondrocytes have their anti-angiogenesis factor is blocked off/inhibited
bring in cells that are FIRST CAPABLE OF DEGRADING THE CARTILAGE MATRIX THEN MAKING BONE MATRIX
first step in long bone formation
bone collar forms around the hyaline cartilage model and a primary ossification center in the middle is formed
second step in long bone formartion
CAVITATION/ degradation of the hyaline cartilage WITHIN THE cartila
ge matrix
- see detiorating cartilage matrix
third step in long bone formation
invasion of internal cavities by the periosteal bud and spongy bone formation
can start to see blood vessel of periosteal bud
fourth stage in long bone formation
formation of the medullary cavity as the ossification continues; appearance of secondary ossification centers in the epiphyses
(in prep for stage five)
epiphyseal blood vessels - in the secondary ossification center
where is the second ossification center seen
in the epiphyses of long bones
stage 5 in long bone ossification
ossificatoin of the epiphyses - when completed - only the hyaline cartilage remains over the epiphyseal plates and articular cartilages
where is hyaline cartilage when long bone ossification is completed
only still persists in the epiphysal plate of the long bone and as articular cartilage at the end of them
what is the mechanism of continued growth in long bones
via ZONE OF PROLIFERATION
zone of proliferation
growth zone - continued lenghtening of the long bones via this center
- cartilage cells undergo mitosis
what is required for control of bone growth
hormones are necessary
when will the epiphyseal plates close?
about at the time of puberty in response to sex hormones
how much of the organic matrix of bone contributes to its weight
45-60% of dry weight of bone is the organic matrix
what is the primary protein in the organic matrix of bone
Type 1 collagen
what is the configuration of the organic matrix of bone
quarter stagger configuration of tropocollagen molecules resulting in “hole regions” in which mineral is deposited
T/F there are non-collagenous proteins of bone in the organic matrix
TRUE
Bone as a morphogenetic matrix implications
Demineralized matrix can induce cellular differentiation
Bone Morphogenetic Proteins - BMP’s
Potential for clinical use
a demineralized matrix can…
induce cellular differentiation through BMP’s - which can stimulate osteoblastic differentiation and bone formation
noncollagenous proteins of bone functions (4 main)
- direct cell binding both osteoblasts and osteoclasts
- control spatial arrangement of mineral deposition
- Control mineral nucleation +/- with temporal control
- Control Rates and sires of mineral resorption
examples of Noncollagenous proteins of bone
Osteonectin Osteopontin Alkaline Phosphatase Growth Factors: PDGF(platalet derived growth factor), alpga 2 macroglobulin Osteocalcin
osteonectin is a?
noncollagenous protein of bone and is a Ca++ binding protein
osteopontin is a ?
noncollagenous protein of bone and known as an “RGD” sequence which stands for arg-gly-asp and mediates attachment
alkaline phosphatase is
noncollagenous protein of bone
growth factors regarding noncollagenous protein of bone
PDGF, alpha- 2 macroglobulin and the major source of this is within the skeleton
osteocalcin is?
what does it contain? implications of production and function
noncollagenous protein of bone and contains gamme-carboxy glutamic acid
DEPENDENT on vitamin D for production and DEPENDENT on Vitamin K for function
GLA produces binding site for calcium
what does GLA produce?
a binding site for calcium - GLA is contained in the noncollagenous protein of bone known as osteocalcin
primary mineral component in bone
calcium phosphate in FORM OF HYDROXYAPATITE CRYSTALS
formula for hydroxyapatite
[ca12(po4)6(OH)2]
what can be substituted into the crystals and implicatoin
other ions like carbonate, fluoride, hydroxyl
substitutions will change characteristics of the the mineral and the composition
control of mineral deposition
nucleation of mineral deposition
crystal growth
T/F enamel does not limitations on growth like bone crystals do
TRUE
- a much larger crystal size is seen in enamel than in bone
initiation of mineral deposition
- increase calcium and/or phosphate concentrations
- removing inhibitors of mineral deposition
- synthesis of molecules as nucleation sites
inhibitors of mineral deposition
pyrophosphate
magnesium
what molecules are synthesized at nucleation sites in favor of initiating mineral deposition
collagen and phosphoproteins
bisphosponate-related osteonecrosis of the jaw
6-11% of patients who have been treated with bisphosphaonate drugs for their cancer (multiple myeloma)
aminobisphosphonates
implication in eventually getting BRONJ - and in patients who have had recent dental extractions
half life for bisphosphonates
up to 12 years -a lot of implications with this
what does bisphosponates do
inhibit the osteoclast function - and can induce apoptosis so remodeling of bone does not occur and brittle bone disease can insue
what do bisphosphonates have a high affanity for
hydroxyapatite crystals
facts about bisphosphonates
analagous to inorganic pyrophosphates with low intestinal absoprtion, secreted through the kidney without metabolic alteration and are incorporated into the skeleton without being degraded
T/F the bisphosponates are degraded
false - they are incorporated into the skeleton without being degraded
