Topic 12 - Osteogenesis Flashcards
What is direct desmal ossification?
Conversion of connective tissue to bone
What is indirect desmal ossification?
Conversion of connective tissue to cartilage and then bone.
Where is desmal ossification observed?
Developing bones of the skull
Fetal development
Healing fractures
(Cartilage is never present)
Describe the process of desmal ossification.
Capillaries invade
Mesenchymal cells become osteoprogenitor cells
Differentiate to osteoblasts
Secretion of osteoid
Osteoblasts surrounded by osteoid become osteocytes
Where does ossification start?
Ossification Centres
Name the space between the matrix and the osteoclast
Howship Lacuna
What is chondral ossification?
Formed by hyaline cartilage, replaced by bone in embryo.
Forms extremity bones - Vertebrae, pelvis
Describe the chondral ossification process.
Cartilage grows at epiphysis
Chondrocytes at diaphysis enlarge promoting calcification
Mesenchymal cells produce bony collar around diaphysis
Capillary loop perforates bony collar
Chondrocytes degenerate, making calcified remains.
Mesenchymal cells bcome osteoblasts, giving out osteoid.
What is found in the resting zone?
Hyaline Cartilage
What occurs in the proliferation zone?
Rows of compressed chondrocytes are formed.
What degenerates chondrocytes?
Chondroclasts (Phagocytes)
What is the epiphyseal plate?
Hyaline below each epiphysis, divide until the end of puberty, later replaced by bone.
When does bone modelling occur?
During growth
Name given to the turnover of bone
Bone remodelling
