MSK 13 - Bone structure, growth and repair Flashcards
what are the two types of bone
spongy and compact bone
what is compact bone in terms of strength and
dense bone strongest part of bone
what are the functional units of compact bone
osteons
where is compact bone found and what kind of stress directions is it able to withstand
on the periphery of bone near the diaphysis
areas with the highest forces - stresses in one direction
what are the functional units of spongy bone
trabeculae
what areas are spongy bone found in and what kind of stress directions is it able to withstand
where we want bones to be lighter
areas where stressors come from many directions
what is the periosteum
fibrous outer membrane of bone
what are the inner cells of the periosteum and what do they allow
progenitor cells allows osteoprogenesis
what process is periosteum important for
bone healing
what is the endosteum
inner lining of bone
every trabeculae is covered in what lining
endosteum
bone marrow is the source of what and what process is it involved in
source of RBC
involved in haemopoesis (blood making)
what is bone storing
fat/adipose tissue
what process is cartilage important for and what does it do
important in bone formation
joints bones together and cushions joints
what are lamallae
layers of bone matrix
what are osteons
single unit of bone
what is the structure of osteons and where are they found
only found in compact bone
structure is concentric rings of lamallae, hollow central canal for blood vessels, osteocytes lie in lacuna and use canciculi to communicate with each other
structure runs in same axis as the force
what are caniculi
channels in bone that allows cells to sit in and communicate with each other
facilitates nutrition
what bone is found in the epiphysis
spongy bone
what bone is found along the edge of the whole bone
compact bone
what is contained in the medullary cavity
marrow and blood
what are the 4 types of bone cells
osteoprogenitor cells
osteoblasts
osteocytes
osteoclasts
what do osteoprogenitor cells develop into
osteoblasts
what is an osteoprogenitor cell
stem cell that will form into an osteoblast
where osteoprogenitor cells found
surface of the periosteum and endosteum
what do osteoblasts do
forms bone extracellular matrix
secretes osteoid
where are osteoblasts found
under the peri or endosteum
what is osteoid
unmineralised bone - mainly collagen
what do osteocytes do
maintains bone tissue by sending messages to osteoblasts and osteoclasts
controls bone metabolism
where are osteocytes found
encased in collagen embedded in bone matrix within its lacunae
as it is encased in osteoid, osteocyte deposits minerals such as calcium salts and hardens the osteoid/bone
what do osteoclasts do
functions in resorption of bone and breakdown of bone extracellular matrix
keeps bone turning over and replaces old bone by secreting acidic enzymes
what does the extracellular matrix of bone comprise of
collagen fibres, mineral salts that forms hydroxyapatite
what is ossification
process of bone formation by osteoblasts
what are the 2 types of bone formation in normal development and growth - not fracture
intramembranous ossification
endochondral ossification
what is intramembranous ossification
bone forms directly from a fibrous membrane
what are the 4 steps of intramembranous ossification and what happens within each step
development of ossification centre
calcification
trabeculae formation
periosteum development
what is endochondral ossification
bone forms from hyaline cartilage template
what are the 6 steps of endochondral ossification
cartilage model developed
growth of cartilage model
primary ossification centre development
medullary cavity development
secondary ossification centre development
articular cartilage and epiphyseal growth plate formation
in endochondral ossification what happens in step 1: cartilage model development
mesenchymal cells develop into chondroblasts, brings in osteoprogenitor cells
in endochondral ossification what happens in step 2: growth of cartilage model
chondrocyte cell division and blood vessels invade
in endochondral ossification what happens in step 3: development of primary ossfication centre
in diaphysis bone tissue replaces most of cartilage as the cartilage dies off as it is too large for nutrition diffusion (enchondral osteoclasts removes cartilage and osteoblasts lay down bone)
in endochondral ossification what happens in step 4: development of medullary cavity
bone breakdown via osteoclasts forms cavity
in endochondral ossification what happens in step 5: secondary ossification centre development
in epiphysis of bone (doesnt happen in every bone)
in endochondral ossification what happens in step 6: articular cartilage and epiphyseal growth plate formation
hyaline cartilage
in intramembranous ossification what happens in step 1: development of ossification centre
osteoblasts secrete organic ECM
in intramembranous ossification what happens in step 2: calcification
mineral salts deposited and ECM calcifies
in intramembranous ossification what happens in step 3: trabeculae formation
ECM develops into trabeculae that fuse to form spongy bone
in intramembranous ossification what happens in step 4: periosteum development
mesenchyme at bone periphery develops into the periosteum and eventually entraps vessels (periosteum, compact bone and spongy bone formed)
bones grow longer via what process and where does this happen
endochondral ossification at the growth plates
bones grow wider via what process and where does this happen
appositional growth on the outer layer and resorption on the inner surface
how does the epiphyseal growth plate grow
cells proliferate from zones of proliferating cartilage in column and pushes the epiphysis up
once cartilage goes up the bone chases it and calcifies cartilage matrix as more bone
what is the epiphyseal growth plate
remnant of cartilage through development
what are the 4 steps of appositional growth when forming a primary osteon
osteoblasts in active periosteum
bone continues to grow ridges come together and fuse to form a tunnel around the blood vessel - tunnel is lined w endosteum
osteoblasts in the endosteum build concentric lamellae onto walls of the tunnel and it is slowly filled inwards toward the centre forming a new osteon
bone continues to grow outwards as osteoblasts in periosteum forms new circumferential lamellae
what is a primary osteon
osteons formed around an existing blood vessel on surface of bone
how does spongy bone grow
grows outwards
where is the blood supply of spongy bone
in the medullary cavity
where is the blood supply of compact bone
blood vessels within haversian canals
how does compact bone grow
grows inwards until it forms a haversian canal
how do osteoclasts form a secondary osteon
osteoclasts bores through existing bone and creates a tunnel inside
osteoblasts move in and line the tunnel wall forming new active endosteum and deposits osteoid on the tunnel walls
layers of new concentric lamallae are put down and blood vessel grows into tunnel to supply active osteoblasts
osteoblasts that are trapped in newly deposited bone become osteocytes and remaining osteoblasts either die or become osteoprogenitor cells and contribute to resting endosteum
what is the difference between creating a primary vs secondary osteon
primary osteons are created on the surface of a bone as it grows while secondary are created inside existing bone
