Bone Flashcards
bone
definition
specialized CT (mineralized, rigid)
living tissue (cells, vessels, nerve fibers)
continuously remodeled
storage for minerals (calcium)
regulates blood calcium levels (via hormones)
supports/protects organs
leverage for movement
remodeling
general
pressure applied
bone reabsorption/breakdown
tension on bone
bone deposition (addition)
orthodontics, treat adults and kids
long bone structure
epiphysis head w/ spongy bone
diaphysis shaft w/ compact bone around marrow/medullary cavity
epiphysis head
surrounded by periosteum except articular surface
membranes of bones
periosteum - around bone
endosteum- inside bone
periosteum
external CT capsule covers outer surface except
articular surfaces and tendon insertions
active periosteum
layers:
outer fibrous = collagen
inner cellular = immature bone cells aka osteoprogenitor and osteoblasts
inactive periosteum
mature
outer fibrous = dense irregular collagen CT, blood and lymph vessels, nerves
-anchored by Sharpe’s fibers to prevent sliding
inner cellular= periosteal cells > osteoblasts if needed for repair
-one layer thick
endosteum
internal CT capsule w/ osteoprogenitor cells and osteoblasts
lines bone marrow cavity, spongy bone
contain haversian and volkman canals for small vessels and nerves to reach bone
inorganic component bone matrix
minerals
hydroxyapatite crystals (calcium phosphate)
bicarbonate, citrate, Mg, Na, K
gives bones hardness
organic component bone matrix
proteins
fibers (collagen I)
ground substance (proteoglycans, glycoproteins, growth factors/BMPs)
cells of bone tissue
mesenchymal stem cells
osteoprogenitor cells
osteoblasts
osteocytes
osteoclasts
from mononuclear hemopoietic progenitor cells
break down/ resorb/ remodel/scuplt bone, miners of minerals from matrix
multinucleated, motile, acidophilic
@ howship lacuna-depression on bone
osteoprogenitor cells
early stage immature bone cells
@ deep layer periosteum and endosteum
osteoblasts
cuboidal shape
synthesize osteoid (organic matrix, pre-bone)
non-mineralized
bone lining cells
flat and quiescent
covere surface to protect from osteoclasts
osteocytes
‘grown up’ osteoblasts
maintain matrix
enclosed in lacuna surrounded by bone then surrounded by osteoid halo
chronic renal failure
CRF
inadequate levels of calcium and phosphate ions so osteoid not mineralized
haversian system
osteocytes enclosed in lacuna w/ cytoplasmic processes branching off in canaliculi oriented toward canal
concentric rings around canal
ECM provides nutrients/oxygen/hormones
small artery, vein, nerves, NO lymphatics
osteoclast regions
ruffled border= resorption, breakdown
clear zone= adhesion, seals around bone w/ actin ring
vesicular= exo/endocytosed material
basal = organelles, nuclei
ruffled border
cell membrane infoldings
exocytosis hydrolytic enzymes
secrete protons into reabsorption compartment to dissolve inorganic matrix
endocytosis of broken bone
clear zone
no organelles
action microfilaments
sealing zone to isolate resorption compartment
vesicular zone
exocytotic vesicles w/ lysosomal enzymes
endocytic vesicles w/ bone breakdown products
basal zone
organelles and multiple nuclei
exocytosis of broken down matrix
organic breakdown
- lysosomal enzymes released by osteoclasts into resorption compartment
- products of breakdown pass into osteoclast for degradation into amino acids/monosaccharides/disaccharides pass into capillaries
- osteoclasts apoptose
gross structure
description
compact-dense, solid
cancellous- spongy, porous
dense bone
haversian systems/osteons w/ concentric lamellae of bone
haversian system is functional unit of compact bone
cancellous bone
irregular bone lamellae
not osteons
skull cap development
outer table= compact, covered by periosteum (pericranium)
center = spongy bone w/ marrow (diploe)
inner table = compact, periosteal layer of cranial dura mater
primary bone
type
immature, woven, random orient collagen
during fetal development and bone repair
temporary and resorbed by osteoclasts
replaced by secondary
lining tooth sockets remains immature thru life
secondary bone
type
parallel or concentric bone lamellae
collagen fibers parallel w/i lamellae
more mineral content than primary
stronger than primary
spongy or compact
lamellar systems
compact bone
outer circumferential lamellae= deep to periosteum
interstitial lamellae= fragments, remnants of old osteons, interspersed w/i haversian
inner circumferential = around bone marrow cavity
rickets
from calcium deficiency or inadequaate dietary supply of vitamin D for calcium absorption
osteiod not mineralize properly so soft bones
osteoporosis
reduction in bone mass = porous
breakdown > formation
lose horizontal trabeculae, thicker vertical
shorter vert. bodies from compression fractures
postmenopausal women
estrogen dec, interleukin 1 & tumor necrosis inc
bone tissue development
environment
- in mesenchyme membrane
2.hyaline cartilage
mechanisms of development
intramembranous (mesenchyme)
endochondral (hyaline)
development steps
- intramembranous OR endochondral
- osteoblasts form primary immature
- resobed my osteoclasts
- replaced by secondary mature SPONGY
- spongy stays spongy or becomes compact
intramembranous
bone directly within membrane of highly vascularized mesenchyme
flat bones
skull is flat bone
endochondral formation
in hyaline cartilage model
long bones
endochondral formation
steps
- hyaline cartilage model with perichondrium
- cartilage grows interstitially and appositionally
- perichondrium vascularized
- signal inner layer to differentiate into osteoblasts
- perichondrium > periosteum
- bone collar form via intramembranous to block diffusion of nutrients
- chondrocytes die
- osteoclasts perforate collar
- periosteal bud enters w nutrients and cells
- osteoprogenitor cells > blasts > osteoid on remnants of calcified cartilage
- hemopoietic form bone marrow
all primary center , diaphysis, before birth
endochondral formation
secondary center
epiphyses, after birth
same process as primary w/o bone collar
cartilage stays in articular surfaces and growth plates (until 18-20)
length growth
via endochondral in growth plates
thickness of plates stays same but distance b/t inc
zone of epiphyseal growth plates
1.reserve cartilage= typical hyaline
2.proliferation= interstitial growth by isogenous groups mitosis, cells inc #
3.maturation
4.hypertrophy ‘popcorn’ glycogen, vacuoles
5.calcification/degeneration
6.ossification= calcified cartilage remnants + newly formed bone + osteoblasts + osteocyte + bone marrow
growth plate additions
bone added to diaphyseal side so pushes epiphysis away
growth in width
bone deposition via appositional added to outer surface
bone resorption via osteoclasts inside
mineralization of matrix
hydroxyapatite crystals take over vesicles from mineral growth
osteocalcin and sialoproteins
bone repair
steps
- trauma
- neutrophils and macrophages clean debris
- Bv’s and fibroblasts grow into blood clot
- granulation tissue forms (LCT)
- DCT and fibrocartilage form
- periosteal osteoprogenitor cells > blasts> osteoid
- bone shell on fibrocartilaginous callus
- osteogenic buds callus
- cartilage calcify > die > replaced
- bony callus replaces fibro callus
- spongy bone forms
- replaced by compact
- remodeled
achondroplasia
clinical correlate
genetic disorder of bone growth= dwarfism
cartilage of epiphyseal plates (proliferation and hypertrophy small)
fibrodysplasia ossificans progressiva
clinical correlate
rare CT disease from autosomal dominant mutation in repair mechanisms
soft tissues damaged > repaired w/ bone = loss mobility, difficulty breathing, prison
may be spontaneous
