Ossification and Bone Disease Flashcards
What does endochondral ossification involve?
The replacement of a pre-existing hyaline cartilage template by bone
What is endochondral ossification the mechanism for?
The development of most of the bones in the body
Where is endochondral ossification particularly important?
Mostly in long bones
Where does endochondral ossification occur?
Foetus
What does endochondral ossification in the foetus form?
The skeleton
What part of long bones become ossified first?
Diaphyses
What is the precursor for most bones?
A hyaline cartilage model
What happens in endochondral ossification?
Cartilage is mineralised to form bone
What do growing bones have?
Growth plates of hyaline cartilage
How long does the femur continue to grow for?
Into adulthood
How does the femur continue to grow into adulthood?
By continuous production of cartilage
On what side does cartilage change into bone in long bones?
Shaft side
What happens after the cessation of long bone growth?
The epiphyseal plate disappears
How much bone is present in a 5-6 week old embryo?
None- it’s purely the hyaline cartilage model
When does endochondral ossification occur?
In a 5-6 week embryo
What happens in a 5-6 week old embryo?
A collar of periosteal bone appears in the shaft
What happens in an 8-12 week old fetus?
- The central cartilage calcifies
- Nutrient artery penetrates
- Formation of the primary ossification centre
What does the nutrient artery provide?
Bone-depositing osteogenic cells
What happens regarding bone development postnatal?
- Medulla becomes calcified bone
- Cartilage forms epiphyseal growth plates
- Epiphyses develop secondary centres of ossification
What happens regarding bone development prepubertally?
Epiphyses ossify and growth plates continue to move apart
What is the result of the moving apart of the growth plates?
Bone lengthening
What happens regarding bone development in a mature adult?
NAME?
How does bone increase in length?
Endochondral ossification
How does bone increase in girth?
Periosteal ossification
What is periosteal ossification?
Intramembranous ossification
What extends from the growth plate when a bone is growing?
Columns of calcified cartilage
What happens to the columns of calcified cartilage in growing bone?
It becomes mineralised
What are the 5 zones of the epiphyseal growth plates?
- Zone of reserve cartilage
- Zone of proliferation
- Zone of hypertrophy
- Zone of calcified cartilage
- Zone of resorption
What is not happening in the zone of reserve cartilage?
- Cellular proliferation
- Active matrix production
What happens in the zone of proliferation?
NAME?
What happens in the zone of hypertrophy?
NAME?
What happens in the zone of calcified cartilage?
NAME?
What is calcified matrix in direct contact with in the zone of resorption?
The marrow cavity
What happens in the zone of resorption?
Small blood vessels and connective tissue invade the region occupied by the dying chondrocytes, leaving the calcified cartilage in spicules between them
What happens are the cartilage spicules in the zone of resorption?
Bone is laid down
Where does intramembranous ossification take place?
Within condensations of mesenchymal tissue
Does intramembranous ossification involve the replacement of a pre-exisiting hyaline cartilage template?
No
What kind of bonds develop by intramembranous ossification?
Flat bones
Give 5 bones that develop by intramembranous ossification?
- Skull bones
- Maxilla
- Mandible
- Pelvis
- Clavicle
How does the clavicle develop?
NAME?
What does intramembranous ossification contribute to?
Thickening of bones at periosteal surface
What kind of growth occurs due to intramembranous ossification?
Appositional growth
What happens in intramembranous ossification of flat bones in the fetus?
Mineral deposits within the many trabeculae radiate outwards from a central point, the early primary ossification centre
Is intramembranous ossification complete in a newborn?
No
What is the advantage of the incompletion of intramembranous ossification in the newborn/
Makes scalp able to withstand trauma
What does the periosteum of newly forming flat bones contain?
Osteoprogenitor cells for bone deposition
What happens to osteoprogenitor cells?
They will merge to form woven immature bone
What does newly formed bone contain?
Bone marrow, blood vessels and mesenchymal tissue
What does compact bone of the skull during postnatal development have?
Osteocytes, osteons, Haversian and Volkmann’s canals
What is the result of the components of the compact bone of the skull during postnatal development being what they are?
Make it indistinguishable from bone arising from endochondral ossification
What is the inheritance pattern of osteogenesis imperfecta?
Autosomal dominant
What is osteogenesis imperfecta a disorder of?
Connective tissue