ossification Flashcards
What is ossification?
A process of laying down bone to a primary ossification centre in cartilage intrauterine
What is secondary ossification?
Secondary ossification centre target the areas primary centre hasn’t reached
Where is the primary centre in a long bone?
In a long bone the primary centre is in the diaphysis shaft in middle
Where is the secondary ossification centre?
The secondary center is in the epiphysis- top and bottom of bone Be careful of the epiphyseal growth plate
What’s osteoporosis?
Osteoporosis- bone loss is at a rate above the norm, accelerated loss of bone mineral density leading to fragile skeleton low bone density score increased risk of bone fracture
Who does osteoporosis mainly affect?
Traditionally post menopause Can affect all ages due to lifestyle choices, illness, medications ect
What type of training helps prevent?
Strength training needed to provide localised changes adding tensile load to proximal end laying down more bony tissue
Osteoporosis T score
T <-2.5= osteoporosis
Osteopenia T score
T<-1.5=osteopenia
Normal T score
T=1.0
When do primary ossification centres appear?
Majority of primary centres appear between the seventh and twelfth week of intrauterine (in the uterus) life virtually all are present before birth
When do secondary ossification centres appear?
Appear after birth in parts of the cartilage model that ossification from the primary centre has not spread
The bone formed by secondary centres are?
almost entirely cancellous
What is a epiphyseal growth plate?
The plate of cartilage between these metaphysics and epiphysis regions
In growing bones, each metaphysis contains an epiphyseal growth plate- a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length.
What happens when the growth plate disappears?
When the bone ceases to grow in length at around ages 12-24 the cartilage is replaced by bone, resulting in a bony structure called the epiphyseal line.
When the growth plate disappears the diaphysis and epiphysis fuse
what does the Endosteum & periosteum produce?
Production of osteoprogenitor cells and osteoclasts
what does an osteoclast do? 3
Remove bone during growth and remodeling (‘osteoClasts ->Cut bone’)
- Osteoclasts help regulate blood calcium levels - They are also target cells for drug therapy used to treat osteoporosis
where is an osteoclast located?
Howship’s lacunae
what do osteoclasts release?
cathepsin K and collagenase
what does an osteoblast do?
Facilitate the mineralization of osteoid matrix (‘osteoBlasts ->Build bone’) and are interconnected via dendritic extensions
what are osteocytes? what do they contain?
Mature bone cells, are the main cells in bone tissue and maintain its daily metabolism, such as the exchange of nutrients and wastes with the blood. Like osteoblasts, osteocytes do not undergo cell division.
Differentiated osteoblasts trapped in the bone matrix
containing cytoplasmic projections with osteoblasts and osteocytes
what cells are found in bones? 4
osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts.
Osteoprogenitor cells 3
unspecialised bone stem cell.
The only bone cells to undergo cell division, the resulting cells develop into osteoblasts,
found along the inner portion of the periosteum, in the endosteum and in the canals within bone that contain blood vessels.
diaphysis
the bones shaft/body long cylindrical main portion
