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Bone

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rigid system of levers, production of soft viscera, storage depot for Ca and P, and houses hemopoetic tissue
What are the functions of bony skeleton?
Epiphysis
What is the end of a long bone called?
Diaphysis
What is the long part of the long bone called?
Metaphysis
What is the cone shaped region that changes shape as we grow?
plates (inner and outer) and diploe (center)
What are the main parts of a flat bone?
more open spaces
What is significant of cancellous (spongy) bone?
less open spaces
What is significant of compact bone?
osteocytes
What do osteoblasts differentiate into?
osteoid, matrix vesicles, cytokines and growth factors
What do active osteoblasts synthesize and secrete?
osteoid
What is the organic portion of the matrix called?
matrix vesicles (alkaline phosphatase and other enzymes)
What are needed for calcification of matrix?
Inactive osteoblasts
What are squamous cells on the bone surface waiting to become active?
Osteocytes
What are surrounded by bone ECM and have numerous cytoplasmic processes such as communication, metabolic exchange, and gap junctions?
maintain matrix through production and resporption, Ca exchange, and respond to changes in mechanical forces
What are the functions of osteoclasts?
Lacunae
What are spaces containing cell bodies?
Canaliculi
What are spaces containing cytoplasmic processes?
Osteocytes
What may revert back to an active osteoblast?
Osteoclasts
What are multi-nucleated giant cells responsible for bone resorption?
mononuclear phagocytic system
Where do osteoclasts belong to?
enzyme secretion, proton pumps to form an acidic environment, and degrade bone matrix
What are the functions of osteoclasts?
resorption bays and resorption canals
What are the spaces called where osteoclasts are found?
bone remodeling
Functions of osteoclasts and osteoblasts are linked during what process?
organic, inorganic
The bone ECM is 50% _____ and 50 % _____.
organic matrix
What part of the ECM is 95% type I collagen fibers, layered parallel within a layer but alternating directions between layers?
PGs, GPs
The organic matrix has ___ such as GAGs like CS and KS and ____ such as osteonectin and osteocalcin.
Osteonectin
Organic GP that is multiadhesive?
Osteocalcin
Organic GP that is calcium binding?
tissue hydration, regulate fiber formation and mineralization, and cell / matrix interactions (metabolism and organization)
What are the functions of PGs and GPs in the organic bone ECM?
enzymes, enzyme inhibitors, chemical signaling molecules
What are the "leftover" ingredients of the organic ECM?
Calcium and Phosphorus
What are the main inorganic constituents of the matrix?
Hydroxyapatite crystals
What are plates along collagen fibers and surrounded by a hydration shell (fluid bound to crystals)?
soft bone
With out non-crystalline minerals what would bone be?
remove organic and inorganic components (if minerals were non-crystalline bone would be less rigid)
What is the role of ECM components?
Lamellar bone
What type of bone is highly ordered, has layers, is mature / secondary, and replaces woven bone?
Woven bone
What type of bone is primary and immature and lacks layers?
Compact lamellar bone
What type of bone has osteon (haversarian system) with a central canal housing blood vessels and nerves?
endosteum
The central canal is lined by what? It means layer of osteoblasts.
Outer and inner circumferential lamellae
What parts of compact lamellar bone do not need osteon structure because there are vessels on the surface and they have no central canal?
interstitial lamellae
What are space between osteons that are leftover from the remodeling process?
Perforating (Volkmann's) canals
What have blood vessels in them going to the central canal?
efficiency (transfer of metabolies and wastes) and strength of bone in multiple directions (from alternating angles, good for tension and torsion)
What is the significance of layered arrangement in lamellar bone?
Spongy lamellar bone
What has trabeculae with alternating layers of bone matrix and cells, cavities between trabeculae filled with highly vascularized bone marrow, and haversarian systems are infrequent?
Woven bone
What type of bone is embryonic and in fracture repair and lacks organization?
less, greater
Compared to lamellar bone, woven bone has _____ mineral content and _____ cell conentration.
Periosteum
What lines the outer surface of bone?
outer fibrous layer
What part of periosteum contains dense connective tissue?
inner osteogenic layer
What part of the periosteum contains osteoprogenitor cells? These can differentiate to osteoblasts and chondroblasts.
vessels and nerve endings (including nociceptors)
The periosteum also contains what?
Perforating (Sharpey's) fibers
What are collagen fibers that bind periosteum to bone and are numerous at tendon and ligament attachments?
Endosteum
What is a single layer of osteogenic cells lining ALL interior surfaces of bone?
nociceptors
Some nerve fibers are in Haversian canals but there are no ______.
Periosteum
Where are nociceptors in bone?
nutrient, metaphyseal, epiphyseal, and periosteal vessels
Name the four bone vessel types.
mesoderm
Bone is derived from where?
mesenchyme
Condensations of _____ form the earliest primordia of all bone.
intramembranous and endochondral ossification
What are the two pathways from initial mesenchyme primordium to bone?
intramembranous ossification
What is direct replacement of mesenchymal condensation?
Endochondral ossification
What is the intermediate hyaline cartilage model?
environment
The only difference between ossification in bone developed from a membranous model and in bone developed from a cartilaginous model is the ______ in which ossification occurs.
intramembranous ossification
Through what ossification type does the development of flat bone occur?
sheets of mesenchyme
In flat bones the development of primary ossification centers occurs within what?
highly vascularized and differentiation of cells to osteogenic cells to osteoblasts
In the primary ossification center of flat bones, what is important?
plates and spicules of bone
Osteoblasts secrete osteoid which becomes ossified and forms what?
osteocytes, osteoblasts
After plates are formed cells become ______. Some cells on surface become additional ____ and process continues.
capillaries, bone marrow cells, undifferentiated cells
Spaces between plates and spicules contain what?
some areas spaces fill in > compact bone, others are cancellous bone
What happens with thickening of bony spicules?
Remodeling
What is the process of woven bone turning to lamellar bone?
Development of ossification centers, formation of plates / spicules, spaces between plates, additional ossification centers form, thickening of plates, and remodeling
What are the 6 steps in development of flat bones?
combo of both
What ossification is used to develop long bones?
intramembranous ossification
Part of long bone development where bone forms under periosteum and the periosteal band (bony collar) is formed?
Endochondral ossification
Part of long bone ossification where remainder of long bone is formed and bone replaces hyaline cartilage?
hypertrophy, resorb matrix, degenerate
Within the bony collar during endochondral ossification condrocytes do what? Also calcification of residual matrix occurs.
periosteal (osteogenic) bud
Where osteoclasts penetrate bony collar and blood vessels grow and osteogenic cells migrate into opening created by osteoclasts?
osteoblasts
What secrete osteoid over calcified cartilage matrix?
remodeling
This process occurs in the primary ossification center and is a combo or resorption and formation, increased density of bone along outer margin, and formation of marrow cavity.
diaphysis
Bone formation continues toward each epiphysis forming the entire _____.
expansion of cartilage
Increased bone length comes from what?
epiphyses
What are the secondary ossification centers?
epiphyseal cartilage plate
This is the cartilage between primary and secondary ossification centers where most of the growth in length of long bones occurs.
Zone of reserve cartilage
What is the resting zone of the long bone?
Zone of cell proliferation
What zone of the long bone has expansion of cartilage and increases length?
Zone of hypertrophic cartilage
What is the long bone zone where cartilage matrix is resorbed, cells accumulate glycogen, there is some addition to overall length, and a thin septa of matrix remain?
Zone of cartilage calcification
What is the long bone zone where remaining cartilage matrix is calcified, calcium and alkaline phosphate, and chondrocyte apoptosis?
Zone of ossification
What is the long bone zone where much of cartilage matrix and cells are removed, capillaries invade, osteoblasts deposit osteoid over calcified cartilage, and there is ossification of osteoid?
Epiphyseal plate
Where does growth in length occur?
under periosteum bone is removed on marrow surface
How is bone marrow cavity diameter increased?
Constant remodeling
What is necessary to maintain the appropriate shape of the long bone?
Compact bone
Where is there layers of osteons added from outside inward and central canal size decreases?
Internal reorganization
Primary haversarian systems > Secondary haversarian systems
loading patterns and nutrition
What is important for bone remodeling throughout life?
calcium
Bone contains 99% of the body's _____.
parathyroid hormone and calcitonin
What regulate blood calcium levels?
parathyroid hormone
What increases bone removal, therefore increasing action of osteoclasts?
Rickets
This incomplete calcification of bone occurs in chilren where bone is easily deformed and there is a decreased rate of bone growth.
Osteomalacia
This incomplete calcification of bone occurs in adults where deficient calcification of newly formed bone occurs, partial decalcification of older matrix, and decreased Ca per unit of bone matrix.
Insufficient dietary Ca or Vitamin D
What causes incomplete calcification of bone?
No
Is osteomalacia the same as osteoporosis?
Growth hormone
What increases liver production of insulin like growth factor?
Gigantism
Excessive growth hormone before fusion of growth plates?
Acromegaly
Excessive growth hormone after fusion of growth plates?
estrogens and androgens
What generally stimulate bone formation and suppress bone removal?
Glucocorticoids
What are used to treat RA and enhance removal of bone and decrease action of osteoblasts?
Mechanical stimuli
What increase bone formation and stimulate osteoblasts?