Skeletal system - Part 2 Flashcards
what does compact bone contain
haversian systems called osteons
how are osteons produced
bony remodeling
what is bony remodeling
removal of existing bone by osteoclasts and redeposition of new bone by osteoblasts
how big are the haversian systems
same size of an osteoclast ~200 micrometers in diameter
what is the outer margin of the osteon deliminted by
cement line
what invades the empty canal
osteoblasts
describe the ultrastructure of compact bone
concentric bony lamellae laid down by successive layers of osteoblasts
how do osteoblasts mature
they get trapped in lacunae in osteoid matrix and mature into osteocytes
what are osteocytes connected by
canaliculi
what do canaliculi use to communicate
gap junctions
what is the center of each osteon
haversian canal
where are the blood vessels and nerves located that supply osteocytes
in the haversian canal
what connects longitudinal haversian canals
transverse Volkmann’s canals
how are waste and nutrients exchanged in compact bone
via haversian vessels
how are haverisian systems oriented in relation to the long axis of bone
parallel along tension lines
what are interstitial systems
inactive Haversian canals
where is the haversian system located
only compact lamellar bone, not spongy woven bone
what is outer periphery of cortical bone arranged in
circumferential lamellae
what covers the periphery of cortical bone
periosteum
what is bone growth controlled by
growth hormone, thyroid hormone, and sex hormones
what are the ways to make bone
endochondral ossification and intramembranous ossification
what happens in endochondral ossification
replacement of cartilage precursor by bone
what is the end result of endochondral ossification
woven bone is extensively remodeled by resorption and appositional growth -> lamellar bone
where is lamellar bone located
long bones, vertebrae, pelvis, and base of skull
what happens in intramembranous ossification
direct replacement of mesenchyme by bone; no cartilage precursor
what do mesenchymal cells differentiate into in intramembranous ossification
osteoblasts that produce osteoid that later mineralizes into bone
what bones are produced in intramembranous ossification and where are they located
flat bones in the vault of the skull
what forms the precursor of long bone
hyaline cartilage
where is the primary center of ossification in endochondral ossification
mid- diaphysis
how is the periosteal cuff formed in endochondral ossification
osteoprogenitor cells and osteoblasts secrete osteoid which mineralizes to form the periosteal cuff
what is the periosteal cuff
thin layer of bone outside cortex
what does the calcification of cartilage matrix inhibit and what does this result in
diffusion of nutrients that results in the death of chondrocytes and spread of osteoblasts
where do osteoprogenitor cells from periosteum migrate in endochondral ossification
into medulla, along with growing blood vessels
where are the secondary centers of ossification in endochondral ossification
epiphyses; mineralization spreads across cartilage matrix
describe the epiphyseal plate in the region of metaphysis in endochondral ossification
it remains open (unmineralized)
what does the open epiphyseal plate allow for
continuous longitudinal growth
what hormonal changes occur at maturity in endochondral ossification
decreased cartilage proliferation and cartilage plate replaced by bone
what is closure of epiphysis and when does it occur
complete ossification, occurs at maturity
what is the last bone to close in humans and at what age
the femur at 18-20
what does the plate look like on Xrays after closure
growth plate is epiphyseal line in metaphysis
what are the zones in transition from cartilage to bone
-zone of reserve cartilage
- zone of proliferation
-zone of maturation
- zone of hypertrophy (and calcification)
- zone of (cartilage) degeneration
- zone of ossification
describe the zone of reserve cartilage and what occurs there
hyaline cartilage with clusters of chondrocytes - no cell proliferation
describe the zone of proliferation and what occurs there
successive mitotic division of chondrocytes -> columns of chondrocytes
describe what occurs in the zone of maturation
division ceases; chondrocytes increase in size
what occurs in the zone of hypertrophy (and calcification)
chondrocytes greatly enlarge, contain large amounts of glycogen, become vacuolated and calcify
what occurs in the zone of cartilage degeneration
capillaries of marrow cavity grow from diaphysis into growth plate
- chondrocytes degenerate; lacunae invaded by osteogenic cells
what occurs in the zone of ossification
blood vessels from marrow cavity grow into cartilage mass
- osteogenic cells differentiate into osteoblasts, congregate on spicules of calcified cartilage matrix to form bony trabeculae
what do mesenchymal cells differentiate into in intramembranous ossification
directly into osteoblasts and begin synthesizing osteoid at multiple sites (multiple centers of ossification)
does intramembranous ossification require a precursor
no
what happens after mineralization in intramembranous ossification
subsequent fusion of adjacent centers of ossification
how do osteoblasts mature in intramembranous ossification
they become trapped in lacunae of osteoid and become osteocytes
what do osteoprogenitor cells do in intramembranous ossification
continue to divide at periphery to provide replacements
what bone is produced in intramembranous ossification
woven bone- later remodeled by osteoclasts and osteoblasts to form compact bone
what is a simple or closed fracture
no break in skin
what is a compound or open fracture
damage to skin exposing bone
what is a comminuted fracture
-bone broken in several pieces
- can be open or closed
what is a hematoma
when blood fills fracture site
what happens immediately after fracture
inflammatory response develops - pain, swelling, redness, heat
what happens in the acute phase of bone repair
neutrophils first to arrive, infiltrate hematoma, then macrophages they both clean up site of injury through phagocytosis
what happens in bone repair after 1 week
fibroblasts and capillaries proliferate and grow into site
what gets formed in bone repair
granulation tissue
what does granulation tissue progess into
becomes progressively more fibrous in chronic phase and forms fibrous granulation tissue
describe what happens to mesenchymal cells in bone repair
they differentiate into chondroblasts, secrete matrix -> progressive replacement of granulation tissue by hyaline cartilage
what is a provisional callous made of
progressive replacement of granulation tissue by hyaline cartilage
what happens in bone repair after the provisional callous
osteoprogenitor cells and osteoblasts from endosteum and periosteum at edge of wound grow inward and produce meshwork of woven bone within provisional callous, deposit calcium salts in collagen matrix
what happens in bone repair after woven bone starts to form
transforms into bony callous that helps to stabilize and bind fracture together
what should a physician do before the bony callous forms
realign and stabilize or set fracture
what is a bony union
when fracture site completely bridged by woven bone
what does bony callous get remodeled into
lamellar bone
how long does bone repair take
6-12 weeks depending on location and severity
what is a synovial joint characterized by
extensive movement
what are synovial joints also known as
diarthroses
what are diarthroses surrounded by
connective tissue capsule
what are synovial joints lined by
thin, discontinuous layer of cells called synovium
what does synovium do
secretes synovial fluid, bathes articular surface
what are synovial joints made of
up to 4 cell layers of synovial cells of mesenchymal origin
- no basement membrane -> not a true epithelium
what are the cells in synovial joints
A and B
what do type A synoviocytes resemble
macrophages
what do type B synoviocytes resemble
fibroblasts
describe nonsynovial joints
limited movement
- joined by dense CT
lacks articular surface
what is a syndesmosis
dense fibrous tissue between bones
what do syndesmosis do in the skull
replaced by bone to become synostosis
what is a synchondrosis joint and what does it contain
-primarily cartilage joint
- contains a single later of hyaline cartilage
where are synchondrosis joints located
unites first rib with sternum, only one in human adults
what is a symphysis joint and what does it contain
-secondarily cartilage joint
- contains two hyaline cartilage surfaces connected by fibrocartilage plate
what do intervertebral joints contain
intervertebral discs
what are intervertebral discs derived from
notochord in chordates
what are intervertebral joints formed of
concentric layers of fbrocartilage
where is the annulus fibrosus
around central core of viscous ground substance, nucleus pulposus in intervertebral joints
what is a herniated disc
damage to annulus fibrosus that causes nucleus pulposus to herniate
what is arthritis
inflammation of joints
what is osteoarthritis
progressive degeneration and loss of articular cartilage
what does osteoarthritis lead to
eburnation, pitting, erosion -> pain, swelling and thickening of joint capsule
what are osteophytes
irregular new bone at edges of articular surfaces
“bone spurs”
what do osteophytes do
limit range of motion
what can the progressive build of of osteophytes, osteoarthritis or trauma lead to
ankylosis
what is ankylosis
bony fusion of joint with loss of mobility
what is rheumatoid arthritis
local, autoimmune reaction in joints -> body produces antibodies that attack joints -> pain, damage to articular cartilage; thickening, inflammation of synovial membrane
what is a pannus
replacement of articular cartilage with fibrovascular tissue
what is gout
deposit of urates and uric acid crystals in joints (especially fingers and toes)
what is gout associated with diet wise
consumption of large quantities of red wine, meat
- asparagus, broccoli, cauliflower, brussel sprouts
- new plant growth or high in protein or nitrogen
what medications can cause gout
diuretics
what happens in rickets
bone matrix doesnt calcify normally in children during growth -> soft deformed bones, can be permanent
what is the cause of rickets
insufficient dietary Ca or Vit D
what can insufficient calcium and Vitamin D lead to in adults
osteomalacia (failure of mineralization) -> softening of bone
what is osteoporosis
loss of bone mass
what happens in osteoporosis (cells)
resorption by osteoclasts exceeds deposition by osteoblasts
what population is osteoporosis common in
post menopausal women, possibly due to decreased estrogen levels
how is osteoporosis treated
with oral calcium supplementation and vitamin D for calcium absorption; chondroitin, glucosamine, gelatin
what does fosamax do
osteoporosis medication, binds phosphates in GI tract to minimize absorption
what is a side effect of fosamax
jaw necrosis
what is necessary for the synthesis of collagen
vitamin C
what is scurvy
vitamin C deficiency where bone matrix is not calcified
how do metabolic bone disorders affect loose teeth
weakens collagen in periodontal ligament
how do metabolic bone disorders affect scars or old wounds
break them open and they bleed
how can metabolic bone disorders be treated through diet
eat fruits and vegetables high in vitamin C such as citrus fruits and guavas
