Bone and Cartilage Flashcards
1
Q
Endochondral ossification make up the bonesof ?
A
- axial skeleton
- appendicular skeleton
- base of skull
2
Q
Process of bone formation in endochondral ossification?
A
- Cartilaginous model of bone is first made by chondrocytes
- Osteoclasts and osteoblasts later replace this with woven bone—>
- then remodel to lamellar bone
3
Q
Membranous ossification make up which bones?
A
Calvarium and facial bones (skull).
4
Q
Process of bone formation in membranous ossification?
A
- Woven bone is formed directly without cartilage.
- Later is remodeled to lamellar bone
5
Q
- Osteoblasts function?
- Osteoblasts differentiate from?
A
- Builds bone by secreting collagen and catalyzing mineralization in alkaline environment via ALP
- Differentiates from mesenchymal stem cells in periosteum
6
Q
- Osteoclasts function?
- Osteoclasts differentiate from?
A
- Dissolves bone by secreting H+ and collagenases
- Differentiate from a fusion of monocyte/macrophage precursors
7
Q
Organic matrix is important to strength of bone. What is matrix made up of?
A
- Over 90% collagen fibers
- ground substance
- mainly proteoglycans, chrondroitin sulfate and hyaluronic acid
8
Q
Bone composition is 30%__ and 70%__?
A
- 30% matrix
- cells maintain and produce matrix
-
extracellular component of bone
- 35% osteoid (organic)
- 65% mineral (inorganic)- hydroxyapatite
- 70% salts
9
Q
What is the major component of bone salts?
A
- Hydroxyapatite (form of calcium phosphate)
- inorganic
- important in deposition of Ca
10
Q
- Collagen in bong is along lines of?
- Important for?
A
- Along lines of tensional force
- Important to tensile strength
- Has high compression strength so bone resists both tension and compression
11
Q
- Extracellular matrix forms most of what kind of tissue
- What is important to density and deformability of matrix?
A
- Forms bulk of connective tissue
- Hydration is important!
12
Q
What are the functions of ECM?
A
- Provides structure and support
- (holds cells and tissues together)
- Limit movement and migration
- barrier to microorganisms and large molecules
13
Q
- What is the most abundant type of protein in the body, especially which form?
- Found in?
A
- Collagen 1
- found in:
- loose connective tissue,
- bone
- tendons,
- skin
- blood vessels
14
Q
Structure of collagen? What does it need to stabilize it?
A
- Triple helix with repetitive nature
- needs vitamin C to stabilize
15
Q
- Lack of Vitamin C means less stability of __?
- Symptoms of Scurvy?
A
- Less stability of collagen and tissues where it is important
- Skin less stable, blood vessels easily injured, gums less stable so teeth are loose
16
Q
- Collagen IV makes a __ rather than fibrils.
- Important in which structures?
A
- Makes a mesh
- important in basement membranes and basal lamina
17
Q
- Glycosaminoglycans (GAG) are repeating __ units with?
- Which glycosaminoglycan is the backbone of the matrix?
A
- Repeating disaccharide units
-
Hyaluronic acid (just disaccharide units)
- bind HA to proteoglycans
- Negative charges bind positive ions,
- H+ bonds to water to form hydrated gel
- matrix is flexible and acts a filter
18
Q
How is cartilage able to be compressed and deformable/regain shape after pressure is released?
A
- High number of negative charges attract cations,
- create high osmotic pressure water drawn in,
- tension balances at swelling equilibrium
19
Q
Function of fibronectin in the matrix?
A
- Proteoglycans bind to fibronectin (besides HA)
-
Fibronectin binds to integrins in cell membranes
- collagen fibrils cells attached to all matrix components
20
Q
How is bone matrix degraded?
A
- Components (GAG) enter cells by endocytosis and fuse with lysosomes
-
lysosomal hydrolase break these down into sugars and amino acids
- lack of any enzyme will prevent degradation and accumulation of partially degraded material in lysosome
21
Q
- Stem cells in bone respond to ___ from osteoblasts?
- These precursors then become osteoclasts that respond to__ and __?
A
- M-CSF from osteoblasts
- precursors become osteoclasts
- responding to IL-6 and RANKL;
- important in osteoclast regulation and bone remodeling/resorption
22
Q
- Osteoclasts are regulated by __ and __?
- What do osteoclasts release against bone surface?
A
- Cytokine receptors (stimulate resorption)
- Calcitonin (inhibit resorption)
Release H+ ions, phosphotases (TRAP) and lysosomal enzymes
23
Q
- Integrins are?
- What type of signals to they transmit?
A
- Transmembrane proteins (alpha-beta dimers)
- connect to matrix and cytoskeleton
- Pass physical signals across cell membrane
24
Q
Role of matrix maetalloproteinasees (MMPs) in degradation of ECM proteins?
A
-
MMP degrade all ECM proteins (locally)
- Important for migration and remodeling
25
Q
Regulation of MMPs in degredatin of ECM proteins?
A
- Synthesized with propeptide that must be cleaved to activate
- TIMP (Tissue Inhibitors of Malloproteinases)
26
Q
On which cells in the bone are the RANK receptor and ligand located?
A
- RANK ligand on osteoblast/stromal cell
- RANK receptor on osteoclast precursor
- Need RANK and M-CSF (always floating around) to differentiate into osteoclast
27
Q
What binds to the RANK ligand on osteoblast/stromal cells and inhibits it’s interaction with RANK receptor on osteoclast precursor cells?
A
- Osteoprotein (OPG) prevents differentiation into osteoclast
- acts as a decoy for RANKL
28
Q
What are other ECM proteins that are not important in bone but are important in skin and other tissue?
A
-
Laminin
- Binds collagen to ECM molecules and cell integrins to provide stability
-
Elastin
- allows blood vessels to deform, lungs to expand and contract without energy
29
Q
Where is elastin found?
A
Abundant elastic fibers found in:
- smooth muscle endothelium near chondrocytes and fibroblast
30
Q
- Chrondroblasts form from which cells?
- Where are they abundant?
A
- Form from mesenchymal cells
- Abundant in the perichondrium
31
Q
- Chondrocyte is defined when?
- What do chondrocytes secrete?
- Abundant in?
A
- Defined when chondroblasts are surrounded by the “matrix” they produce
- Sit in lacunae
- Secrete Type II collagen and extracellular matrix
- Abudant lipids, glycogen and RER
32
Q
Extracellular matrix (“ground substance”) consits of?
A
- Hyaluronic acid
- glycosaminoglycans
- chondroitin sulfate
- keratin sulfate
It is extremely hydrated
39
Q
Fibrocartilage is comprised of?
A
- Chondrocytes and firbroblasts
-
Type I and Type II collagen
- less water and proteoglycans than hyaline cartilage
67
Q
- What is the synoviam?
- What does it contain?
A
- Outer layer of dense connective tissue (in joint capsule)
- Inner synovial membrane with 1-2 layers of synovial cells
- NO basement membrane
- NO tight junctions
- Fenestrated capillaries
