What is the major supporting framework of the body?
Bone is the major reservoir for___-
soluable salts must be transported from blood vessels to osteocytes by...
canaliculi because deposits of calcium int he matrix prevent diffusion of soluble salts
what are the two forms of bone?
compact dense bone spongy trabecular/cancellous bone
What are the organic components of bone?
type I collagen (90%) proteoglycans and other proteins (10%)
What do the organic components of bone contribute to the structure?
What are the inorganic components of bone?
calcium phosphate (hdyroxyapatite crystals)
What do the inorganic components of bone contribute to the structure?
What type of growth does bone illustrate?
appositional only (periosteum)
most bone except articular surfaces insertion of tendons insertion of ligaments
shaft primarily compact bone with marrow cavity at center
bulbous expanded ends of bone primarily spongy bone covered by thin layer of compact bone
funnel shaped region that connects diaphysis with epiphysis SPONGY BONE
separates epiphysis from diaphysis cartiligenous connected to diaphysis by spongy bone (metaphyssis) RESPONSIBLE FOR INCREASE IN LENGTH OF GROWING BONE
osteoclast bone reabsorbtion
acidic environment lose rigidity
What are the two types of bones?
Compact bones or trabecular
Where is the outter circuferentia lamellae?
It is located under the periosteum, and it is the external surface of the compact bone.
What type of bone is the intersitial lamellae?
Compact lamellae haversian
What type of bone is the outter circumferentia lamellae?
compact lamellae non haversian
What type bone is the inner circumferentia lamellae?
compact lamellae non haversian
What does non haversian mean?
It does not have any blood vessels in the center.
What type of bone is bone marrow?
Trabeclar lamellae non haverian
How do periosteal and endosteal communicate with the haversian canal?
Through the volksmanns canal
It is made by osteoblast. It helps with the mineralization of the bone.
What type of bone is the haversian system/ osteon?
compact lamellar haversian bone
Where is the inner cirucmferential lamellae found
under the endosteum
lines marrow cavity and spaces in spongy bone
become osteoblast when repair is necessary (fractures)
Intersistial lamellae are round
between osteons and separated fromt hem by cement line
Outer layer of perisoteum
alot of collagen and blood vessels then penetrate volksmanns canal
Inner layer of Periosteum
Lined with osteoproginator cells
Non Callgenous Matrix Proteins of bone matrix
inhbiits osteoblast function/ bone mineralization
made by osteoblast
properties in mineralization of bone
What type of growth does bone exhibit
Where are sharpeys fibers seen?
outer layer of periosteum
What do sharpays fibers do?
thick collagen fibers that penetrate outer layer of periosteum
How do the cirumferential lamellae (non-haversian) get their nutrients and excrete waste?
the osteocytes exchange nutrients and waste products with blood vessels in the marrow cavity
Where are osteoprogentiro cells found?
in inner layer of periosteum and endosteum
bone lining cells (osteocytes) but reactivate during repair of bone fractures and other injuries
Where do osteocytes reside?
lacunae of concentric lamellae
arranged between lamellae
and interconnected by canaliculi
What does the cement line separate?
haversian canals from interstitial lamellae
osteoblast are derived from
Osteocytes are derived from
monocyte-marcophage lineage in bone marrow
osteocytes become trapped in the
calcified matrix of the lamellae (lacunae)
What interconnected adjacent lacunae?
What type of junction interconnects canaliculi
gap junctions (ions and low molecular weight molecules)
How do high moelcular weight molecules pass between cells
via diffusion through the extraceullar mediumin the canliculus surrounding the filopodia
formation of sealing zone
mediates binding of osteoblast to ECM through integrins
soft tissue under osteoblast
non-mineralized organic matrix
unlike bone has no calciumphosphate
terminally differentiated cells in charge ofmaintaining the ECM of the bone
control mineralization fo the matrix
control differentiation of the osteoclast (RANKYL)
What are hte major protein products of osteoblast
type 1 collagen
RANKL (osteoclast precursor cells)
osteopontin (formation of sealing zone)
bone sialprotein (mediate bonding of osteoblast to ECM through interins)
The differentiation of osteoblast to osteocytes are regulated by
1. Bone morphogentic protein
2. Transforming growth factor beta
3. cbfa1/runx2 (Transcription factors )
4. osterix (TF)
ectoenzyme (surface protein)
reacts strongly with osteoblast but disappears when osteoblast ceases protein synthesis ( becomes osteocytes)
Vitamin D (osteoblast)
regulates expression of osteocalcin (mineralzation with Calcium)
growth hormone ( osteoblast)
produces IGF-1/somatomedian C which stimulates growht of long bones at level of epiphyseal plate
simtulates osteoclast of break down bone and release Calcium
receptor for activation of nuclear factor kappa B ligand (nf-kb) present in osteoclast precursor cellls
life of bone matrix depends on
ARe osteoclast uninuclear or multinuclear?
Where are osteoclast found?
howships lacunae/substeocalstic compartment
osteoclast create what type of environment?
acidic- required for bone reabsorbtion
dissolution of inorganic parts of bone (rigidity) bone demineralization
followed by enzymatic degradation of organic matrix (by protease cathepsin K)
rich in mitocondria and acidified vesicles
ruffled border (active surface facing lacuna)
Osteoclast activity is regulated by
regulatory moedlcules of osteoblast and stormal cells of bone marrow
where is the ruffled border of the osteoclast?
Where is the sealing zone of the osteoclast?
What contributes to the sealing zone of osteoclast
alpha v beta three integrin
What mechanisms do osteoclast have to maintain
the intergrit of its ph and the cytoplasm around it?
HC03- / CL Exchangers to pump out bicarbonate and maintain cytoplasmic electroneutrality
cloride channels to pump out cl- and maintain the acidity of the osteoclast and howships lacune
carbonic andydrase Ii (generates prtons from (co2+h20-> hc03- + h+) the h+ is relased to howships lacuna by h-atpase pump to create acididc environment )
Cathespin K released into howships lacuna to degrade epxosed organic matrix (collagen)
What is the purpose of the sealing zone?
keeps the contents inside the howships lacuna
Osteoblast are active in repsonse to calcium mobilzation in from the bone to blood
because it breakd down bone
when there is less vitmain d what happens to osteoclast activity
it goes up
osteoclastogenesis (osteoclast differenentiation) is triggered by 2 molecules
macrophage colony stimulating factor (MCSF)
nuclear fator kappa (NF-kb) ligand (RANKL)
describe osteoclast development
1. there is a monocyte with a MCSF receptor on it
2. The osteoblast releases MSSF (macrophage colony stimulating factor ) LIgand which attaches to the receptor on the monocyte
3. this in turn , transforms the monocyte into a macrophage
4. this binding induces th eexpression of RANK which will will bind to RANK ligand epressed off the surfact of the osteoblast
5. the mononucleated monocyte becuase hte mutlinucleated osteoclast precursor but still does not have the ability to absorb bone
6. The resting (nonfunctional osteoclat uncouples fromt he osteoblast)
7. osteoblast maturation is completed when the sealing zone of the ruffle border appears
how is osteoclatogensis inhibited
by osteoprotegerin (from osteoblast) by blocking RANKL binding to receptor
high bone density due to absent osteoclastic activity
stone like bone
lack of MCSF
can lead to occlusion of marrow spaces and anemia
excessive osteoclastic activity and deficient osteoblastic activity
Menopause- defc in estrogen
treatment with calcium and vitamin b
defect in mineralization
vitmaind d deficiency (rickets)
chronic kidney disease
increased bone mass due to increase osteoblast activitiy
functions like osteoprotegerin
bone is deposited directly within embroynic connective tissue