development and growt of bone Flashcards
what are the functions of bone
support body shape
system of levers for muscle action
protection of internal organs eg ribs and pelvis
site of blood cell formation - marrow
mineral storage pool - ca
what are the machanical properties of bone
cable like flexibility and resistance to tension - because framework is collage and other bone proteins (this is the osteoid)
pillar like stiffness and resistance to compression - because of impregnation of collagen with cyrstalline mineral hydroxyapatute (complex ca hydroxyphosphate)
what are the 2 types of bone tissue
woven (immature bone) - formed in healing, early stages of repair
lamellar (mature bone)
describe how you can see the structure of lamellar bone and what it is
use polarising microscopy - show up when tings are aligned
sow the concentric lamellae around the central canals
describe the structure of woven bone
random arrangement - needs to be remodelled to form lamellar bone
what is the arrangement of bones
have head at either side of the bone
articular cartilage on both heads
shaft (diaphysis) is between the heads
medullary cavity in diaphysis - marrow here and makes bones lighter
nutrient arteries leave and enter through nutrient foramen/canal - veins run with them
outer hard layer of compact bone - cortical bone
inner layer of interlacing spikes of lamella bone tis is cancellous bone (spongy/trabecular bone) - like a meshwork
describe the arrangement of lamellar bone
spongy bone is strong because te interlocking tubercles old it together and distribute force - however, not as resistant to compression as compact bone
compact bones made of ostions - a column of bone with bv and nerves running through middle (central canal) - around here have concentric cells
between the circles have interstitial lamellae - still lamellar bone
trabecular are made of lamellar bone even though irregularly arranged
osteocytes have protusions connecting to other cells via gap junctions so cells sare the nutrients from the central canal
ave ca deposits
what is periosteum
it is te outer surface of bone - a fibrous and cellular layer
involved in bone growth and repair - osteoblasts develop from cells in the periosteum
vascular
sensory nerve supply - what causes pain from fractures
describe the generation of osteocytes
osteogenic cell develops into an osteoblast which forms bone matrix and turns into an osteocyte whic maintains bone tissue
describe osteoclasts
function is bone resorption, the breakdown of the bone matrix
multinuclear
ruffled border
similar lineage to macrophages
how long are bones growing
skeleton forms from 6 weeks in foetus bup to 25 yrs of age
what are the 2 types of ossification
intramembranous
endochondrial - more common
describe intramembranous bone development
in existing vascular connective tisssue - signals to develop into bone
calcified bone matrix proteins (ostein) is deposited around collagen
mineralises to form woven bone
vascularised
remodels to form lamellar bone
used for the flat bone of the skull and mandible
describe endocondrial bone development
within existing fetal cartilage models - short small version of early cartilage
cartilage calcifies and condrocytes die
periosteal osteoclasts cut channels for sprouting vessels
osteoblasts enter with vessels to build bone around them
what is the thing you need to overcome for bone growth and how is it overcome
long bones support forces whilee growing
if tried to grow at end these forces would disrupt te terminal appositional growth because of the articulates
solution;
shaft ossifies first then the epiphyses
growth continues by ossification of growing cartilage plate between them
growt cessation occurs when cartilage growt ceases and plate overrun by ossification
describe endochondrial ossification
have calcified matrix which attracts bv
osteoclasts remodel bone
there is a secondary ossification centre in the head
cells are arranged in a column, proliferate and push the head forward
teh epiphysial plate remains cartilage until late
epiphysial surface not affected - bone can still support weight
describe te age related change in appearance of normal bones
in wrist epiphyses ossify in 2nd year
the epiphyseal plates remain cartilaginous until after puberty, growth occurs here until hormones tell it to ossify
what is te effect of a child breaking their hand at an epiphysial plate
affect growth
have to scaffold it in place to ensure normal growth
give examples of how bone is adaptable
can grow witout comprimising func
increase/decrease bulk and density depending on its pattern of use
can alter internal and external shape in response to pattern of use = remodelling
repair when fractured
how can bone remodel
bone has a large blood supply - cells near o2 and nutrient source and waste removal
osteocytes maintain matric but can activate osteoblasts for new bone building
osteoclasts giant cells specialised for destruction of bone matrix
describe te growth of bone diameter
it is called apposition
cells in the periosteum activated to become osteoblasts and produce new bone
osteoblasts and osteoclasts create ridges and grooves on the bone surface
bv align in the grooves
ridges fuse around the vessels
osteoblasts build new osteons round vessels
osteoclasts remove bone from the endosteal surface
describe fracture healing
fractures damage bv = haemotoma - this is the first part of healing
osteoprogenitor cells and inactive osteoblasts from periosteum and endosteum differentiate into aactive osteoblasts and migrate to fracture
the migrating osteoblasts form a provisional type of bone and cartilage called the external callus - this bridges the end of bones. internal callus forms between bone ends
connective tissue and bv invade clotting region
chondrocytes produce cartilage that is replaced by bone
forms woven bone
this is remodelled to form lamellar bone (first cancellous then cortical) - reactive cartilage undergoes endochondrial ossification
what happens if blood ca levels are high
calcitonin released by parafollicular thyroid cells - osteoclasts inibited - ca uptake into bone promoted
what happens if the blood ca levels are low
pth released by chief cells of parathyroid gland - osteoclast bone resorption promoted - increase ca resorption in kidney - ca released into the blood
what effects bone remodelling *
physical stresses
metabolic and hormonal factors
