Bone development Flashcards
what are the different layers of the bone?
- periosteum
- compact or dense tissue
- spongy or cancellous tissue
- bone marrow
What are the functions of osteoclasts?
- bone resorption
- phagocytosis
- antigen representation
- immune modulation
- T cell activation
What 3 fates do osteoblasts have after bone formation?
- flatten and remain quiescent lining cells at the bone surface
- die by apoptosis
- become surrounded by bone matrix, that calcifies trapping the cells. results in lacunae
What do osteocytes do?
they maintain bone tissue by controlling mineral and calcium content. secrete sclerostin to activate or inhibit osteoclasts.
what type of cartilage do we have?
- hyalin cartilage
- elastic cartilage
- fibrocartilage
what is the function of hyalin cartilage?
lines the joints and caps, reduces friction
what is the function of elastic cartilage
most flexible cartilage, supports parts of your body that need to bend and move to function
what is the function of fibrocartilage
tough cartilage, made of thick fibers, holds body parts into place and absorbs impact.
what are the 3 zones of hyalin cartilage?
- superficial zone > smooth contour, highest collagen content of all zones
- middle zone > collagen fibrils are thicker and align loosely, not parallel to surface
- deep zone > highest proportion proteoglycan, lowest concentration water. chondrocytes arranged in columnar fashion
What do the somites generate in development?
the axial skeleton
what does the cranial neural crest generate in development?
the branchial arche
What 2 processes are used to develop different parts of the skeleton?
- intramembranous ossification
- endochondral ossification
What is intramembranous ossification?
osteoblasts produces bone within connective tissue membrane.
what is endochondral ossification?
Production of bone within cartilage scaffolds, arranged in zones, gradually replaced by bone.
What are the 4 stages of fracture repair?
- hematoma formation
- fibrocartilaginous callus formation
- bony callus formation
- bone remodelling
What are the zones of the growth plate?
- zone of reserve cartilage
- zone of cell proliferation
- zone of cell hypertrophy
- zone of calcification
- cone of bone deposition
What are the steps of bone resorption?
- attachment
- seal bone-ruffled membrane
- acidification to pH 4,5
- mineral mobilisation and removal by TRAP
- degradation of ECM by cathepsin K
- removal of fragments by TRAP
What is appositional growth?
Growth in diameter of bones around the diaphysis occurs through the deposition of bone beneath the periosteum. Osteoclasts in the interior cavity continue to degrade bone until its ultimate thickness is achieved. At this point the rate of formation on the outside and degradation from the inside is constant
What is sialprotein?
a component of mineralised tissues that acts as a nucleus for the formation of the first apatite crystals.
What is osteocalcin?
secreted solely by osteoblasts, it is pro-osteoblastic and is implicated in bone mineralisation and calcium ion homeostastis
What is SOX 9 for?
For production of type II collagen, base of hyalin cartilage
What happens if SOX 9 is not present?
embryo is not viable, limbs will not develop
What is Run X2 for?
for production of collagen type X, a network forming collagen and for enlargement of cells > hypertrophy
What happens if Run X2 is not present?
Without Run X2, all bone will remain cartilage
What does MMP-13 do?
breakdown of cartilage in osteoarthritic joints.
What are the steps of endochondral ossification?
- mesenchymal cells differentiatie chondrocytes
- cartilage model of the future bony skeleton and the perichondrium form
- cappilaries penetrate cartilage. perichondrium transform into periosteum. development of primary ossification center
- cartilage and chondrocytes continue to grow at ends of the bones, development of secondary ossification
- ossifcation of the epiphysis, cartilage remains at epiphyseal plate and at joint articular cartilage
What is the composition of CEM(Cartilage extracellular matrix)
- collagen type II
- proteoglycans
- hyaluranic acid
- water
- glucosaminoglycans(GAGs) like keratan sulfate and chondroitin sulfate
What is articular cartilage?
permanent cartilage
what is transient cartilage?
temporary cartilage, involved in bone growth
