unit 5 Flashcards
what is the origin of chondroblasts? where are they located?
paraxial mesoderm
located in the periphery
what is chondrogenesis?
matrix producing during development and growth
what is appositional tissue growth?
when chondroblasts secrete new matrix along existing surfaces, causes cartilage to expand and widen
what is the origin of chondrocytes? where are they located?
chondroblast
central/deep location
what are chondrocytes the primary cell for?
primary matrix producing cells within mature cartilage resulting in interstitial tissue growth
what is interstitial growth?
chondrocytes secrete new matrix within the cartilage, grows the bone in length
what is the composition of cartilage?
semi-solid, not highly organized with randomly dispersed cells
aggrecan-hyaluronan aggregates and cartilage-specific collagen molecules
why is cartilage firm yet pliable?
due to interaction of GAGs and PGs
what type of collagen molecules are found in cartilage?
type II collagen, and VI, IX, X, and XI
why is a semi-solid composition in cartilage important?
crucial for diffusion of nutrients and waste
cartilage is…
avascular and aneural
what is a lacunar space?
void space in cartilage where a cell resides
located in the ECM, accommodate chondrocytes
isogenic groups
regions where chondrocytes sit next to each other
represent cells that have recently divided
capsular (pericellular) matrix
directly surrounds lacunae, stains darkest
high concentration of PGs, GAGs, MAPs
territorial matrix
surrounds isogenic groups, stains in the middle
interterritorial matrix
occupies space between IGGs, stains light
what determines the intensity of cartilage matrices?
proximity of produced micromolecules
where is hyaline cartilage found?
articular surfaces of synovial joints, costal cartilage, nasal cavity, larynx (thyroid, cricoid, arytenoid), trachea, bronchi, fetal skeletal tissue, epiphyseal plates
where is fibrocartilage found?
IV discs, pubic symphysis, articular discs, menisci of knee, wrist joint, insertions of tendons
where is elastic cartilage found?
pinna of external ear, external auditory meatus, auditory tube, larynx (epiglottis, corniculate, cuneiform)
hyaline cartilage
most common, weakest
staining appears homologous
what is hyaline cartilage surrounded by? what can it undergo?
perichondrium
calcification (endochondrial ossification at epiphyseal plate)
what does type II collagen do for hyaline cartilage?
allows it to withstand pressure
fibrocartilage
less cellular, less able to repair and regenerate, NO perichondrium
type I collagen
why is type I collagen important in fibrocartilage?
helps with tension
structure of collagen forces the chondrocytes into linear rays
elastic cartilage
type II collagen, GAGs, PGs, GPs, elastic fibers, lamellae
what is osteoarthritis?
mechanical breakdown of cartilage
chondrocytes are worn away, the tissue loses the ability to retain water
what is articular cartilage
hyaline cartilage covering a moveable joint
more organized with NO perichondrium
articular cartilage
what is the origin of osteoblasts? where are they located?
mesoderm or ectoderm
bone surface
how do osteoblasts contribute to bone formation?
they cover themselves in osteoid which is then mineralized around them
what is the origin of osteocytes? where are they located?
osteoblasts
in lacunar spaces where matrix isn’t ossified
what allows for osteocytes to do mechanosensation?
fluid moving through lacunar-canalicular network
what do lacunar-canalicular networks allow for?
communication between adjacent cells and free surface cells
what is the origin of osteoclasts? where are they located?
lateral mesoderm
bone surface
what are osteoclasts?
bone macrophages, monocyte that left circulation to participate in bone resorption
organic composition of bone
type I collagen, BMPs, CBPs, MAPs, ALP
allows the bone to stretch to a point
inorganic composition of bone
calcium phosphate forming hydroxyapatite crystals
allows for compression resistance
bone is…
vascular and neural
arteries branch in central and perforating canals
what do calcium binding proteins do?
bind extracellular Ca2+ which stimulates osteoblasts to secrete alkaline phosphatases
what do alkaline phosphatases do?
increase local concentration of PO4 ions, further increases the Ca2+ concentration
what do osteoblast ectosomes do?
accumulate Ca2+ and PO4, assemble hydroxyapatite crystals
what do bone matrix proteins do?
contribute to formation of ECM collagen scaffold for mineral deposition
what do hydroxyapatite crystals do after they exit the matrix vesicles?
develop as mineralized nodules within the ECM collagen scaffold
what does the ruffled border of the osteoclast do?
increases SA, which in turn increases proton secretion and hydrolytic enzyme exocytosis
what does increased proton secretion lead to?
decalcification
what does increased hydrolytic enzyme exocytosis lead to?
collagen degradation by cathepsin K
what is the clear zone?
tight seal between osteoclast plasma membrane and bone matrix, ensures mineralization is localized
what is the basolateral region of the osteoclast for?
exocytosis of bone debris
osteoporosis
imbalance in bone producing osteoblasts and bone resorbing osteoclasts
bone resorption> bone formation
what is an osteon?
function unit of bone
bone organization
how is bone classified?
by organization
trabecular or cancellous bone
spinuols of bone
compact bone
plate of bone
endochondral ossification
mesoderm -> paraxial mesoderm -> somites -> cartilage -> bone
most axial and appendicular bones
endochondral ossification steps
cartilage model
periosteal bony collar
cartilage matrix mineralized
blood vessel formation & periosteal migration
cartilage matrix reabsorbed and replaced with bone matrix
(most axial and appendicular skeleton)
https://www.youtube.com/watch?v=YXDyQiVepWk
intramembranous ossification
ectoderm –> neural crest –> mesenchyme –> bone
flat bones of skull and face
interstitial growth
cartilage resorption and bone deposition
osteoclasts and osteoblasts work together
appositional growth
uncoupled bone resorption and formation
“bone modeling”
osteoclasts and osteoblasts work independent
what can cells in the zone of reserved cartilage do?
go through mitosis
epiphyseal growth plate layers
zone of reserved cartilage
zone of proliferation
zone of hypertrophy
zone of calcified cartilage
zone of resorption (primary spongiosa)
how can bone remodeling be described?
stochastic (random) or targeted
stochastic bone remodeling
osteoblast actives -> osteoclast resorbs -> osteoblast forms
targeted bone remodeling
repair microcracks
osteoclasts bore a hole in bone to get to crack, form a cutting cone, osteoblasts form bone
what does bone maintenance require?
mechanical stimulation
woven bone formation
osteoblasts can’t keep up with the demand so osteoid is laid down in an unorganized manner
when are osteoblasts and osteoclasts equal
in bone maintenance
when are there more osteoblasts than clasts?
bone formation, woven bone formation
when are there more osteoclasts than blasts?
disuse bone loss
calcium regulation via PTH
how is a bone fracture healed?
