Bone Hard 🍆💦 Flashcards
Osteoid =
Made by
What is in
Looks
Extra cellular matrix Secretes by osteoblasts Type 1 collagen Gags and proteglycans Pale pink histology
Resorption cavities=
Howships lacunae
Depressions that osteoclasts create
Osteon=
Central Haversion canal with blood vessel. This canal surrounded by concentric rings of lamellar bone w osteocytes
Haversion canal=
Route for blood vessel within bone
Clavicle is annoying. Why
It’s a frickin flat bone !
Osteoblasts secretes what
Osteoid and RANK L
Volkmanns canal=
Canal for blood vessels that runs perpendicular to Haversian canals/osteons , connecting them up.
Effect of rank L
Activates osteoclasts.
Attached to osteoclast precursor (monocyte) allowing them to go and remodel bone. Because it allows the rank ligand to bind to the rank part of monocytes/osteoclasts
What blocks activation of monocytes-> osteoclasts
OPG
Osteoprotegrin
What does OPG block
It stop activation of osteoclasts by stopping rank ligand binding to rank(on the osteoclast itself) as opg binds to the rank ligand itself
What is opg used to treat
Bone loss, osteoporosis
It lowers osteoclast activity so less bone chewwwwed
How many layers of cells in synovial joints
1-4
Types of cells in synovial joints
Type A - phagocytes
Type b- rich in RER, secrete synovial fluid
What inhibits bone resorption
Bone resorption is chewwwing by osteoclasts
So OPG
And calcitonin
Long bone formation
Endochondrial
- from cartilage to bone
Flat bone (and irregular bone) formation
Intramembranous
- from mesenchymal cells
Ossification centres =
Bone laid down (osteoblasts) on top of hyaline cartilage (chondrocytes)
Primary= middle of bone Secondary= ends of bone
What happens to ossification centre
Osteoclasts break down to leave a medullary cavity
Mineralisation
When
What
Regulated by
Intramembranous ossification
Hydroxyapatite crystals laid down (calcium and phosphate)
Hardens bone- spicules created which then fuse to trabeculae
Vit d and PTH
Healing
Direct-
Osteoclasts cute tunnels and osteoblasts fill them in, across fracture
Stable fracture
Healing
- / indirect
4 stages
Unstable fractures
1 inflammation- haemotoma (clotted blood swelling inc wbc) stabilises
2 soft callus formation - fibroblasts and collagen , replaces haemotoma
- Hard callus formation- endochondrial ossification to create woven bone
- Remodelling - woven bone becomes lamellar
Macro bone types
Corticol = compact , dense
trabecular- spongy, cancellous. (Light) Holes . Often filled with bone marrow
Micro. Bone types
Primary/ woven— made quickly, disorganised
Secondary - lamellar/- made slowly, layered . Replaces woven
