Lec 13 Bone Development Flashcards
What is an osteoblast?
cell that build bone; derived from mesenchymal stem cell in periosteum
secretes collagen and catalyzes mineralization
What is an osteoclast?
multinucleated; much bigger than osteocyte; breaks down bone
What is an osteocyte?
bone cell; senses mechanical force/stress on bone
What type of collagen do osteoblasts secrete?
type 1 collagen
What can you use to measure level of osteoblast activity?
- alkaline phosphotase
- osteocalcin
What is effect of calcitonin on bone development?
inhibits osteoclasts
What is effect of PTH on bone development?
activates osteoblasts
What is effect of insulin on bone development?
activates osteoblast to stimulate matrix synthesis
What is sclerostin?
protein that has inhibitor effect on osteoblastic activity; when osteocyte senses micro-crack –> stop producing sclerostin so build more bone
Where does osteoclast reside?
at ruffled border
What is RANK?
receptor on osteoclast precursor; binds RANK-Ligand [RANK-L] on osteoblast which activates it
What is osteoprotegerin?
protein on osteoblast that blocks RANK so that osteoblasts can inhibit osteoclasts
What is function of diaphysis?
thicker cortex, less trabicular bone
What is function of metaphysis?
aids in stabilization
How does bone grow in width?
resorption from middle; growth outside = maintains central hollow portion
What do cement lines represent?
signs of where old surface of bone was before growth/remodelling
What happens to cement lines in pagets?
become very irregular
WHat is first step in skeletal morphogenesis?
cartilage formation
What is endochondral ossification?
replacement of cartilage with bone; main way that skeletal forms
When does epiphyseal growth plate remain open until?
until full maturity at age 19-20
What is intramembranous ossification?
directly form bone from fibrous periosteal layer
What type of bone makes up cortex?
mostly compact
What type of bone makes up medullary?
cancellous/trabecullar bone –> have space that is occupied by fat/red marrow
What parts of skeleton have marrow in adults?
only axial skeleton
What is difference woven vs lamellar bone?
woven bone is immature; less organized; suggests pathology
lamellar = more stable, organized
What type of joints are synovial joints?
diarthrosis
What kind of ECM is secreted by chondrocytes?
made up of type 2 collagen + proteoglycans
WHere is fibrocartilage located?
in intervertebral disc; meniscus
Where is elastic cartilage located?
ear
What are type A vs type B synoviocytes?
type A = phagocytic
type B = secrete synovial fluid
