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Aleksbaron
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Collagen is the most abundant _______ protein
fibrillar
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_______ are the principle cell in connective tissue.
Fibroblasts
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________ substance is primarily responsible for the ________ and filtration function of connective tissue.
- Ground substance
- viscoelasticity
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Ground substance is mainly composed of?
Proteogylcans (Protein core and GAG)
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Adhesive glycoprotein?
Fibronectin
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List layers of pulp from peripheral.
- Odontoblastic layer
- cell free zone or zone of Weil
- cell-rich zone
- pulp proper
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List the main components of the odontoblastic layer
- Terminal capillary network
- Nerve fibers (terminal axons from plexus of Rashkow) between odontoblasts
- Class II MHC dendritic cells
- Korff fibers
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List main components of the cell free zone.
- unmyelinated nerve fibers
- blood capillaries
- process of fibroblasts
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List main components of cell rich zone.
- Fibroblasts (more here than pulp proper)
- undiff mesenchymal cells
- defense cells (macrophages/lymphocytes)
- blood capillaries
- nerves
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How can Korff fibers be identified histologically?
Silver impregnation
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List components of pulp proper.
- Fibroblasts (most abundant cell type)
- Larger blood vessels
- Nerves
- Undiff mesenchymal cells
- defense cells like macrophages (in perivascular area)
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Collagen fiber bundles are more numerous where?
Root pulp, therefore clinical implication of barbed broach
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What is meant by low-compliance environment of the pulp?
It is encased in rigid mineralized tissue
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What is the self-strangulation theory?
Increased tissue pressure caused blood vessel compression and resultant ischemia and pulpal necrosis
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What physiologic mechanisms does the pulp have to combat the strangulation theory?
Feedback mechanisms to oppose inc. in tissue pressure (inc. lymph flow and absorption of interstitial fluid into capillaries in non-inflamed areas)
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Which neuropeptides modulate vasodilation in the pulp?
substance P, CGRP, neurokinin A
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What are the efferent properties of the pulpal sensory neurons when using substance P and CGRP?
- modulate extracellular matrix production
- secondary dentinogenesis
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Collagen domain?
Triple helical
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Collagen chains?
α chains
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Collagen assembly?
- 3 polypeptide chains
- hydrogen bonds
- hydrophobic interactions
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Collagen distinct two amino acids?
- Hyroxyproline
- hydroxylysine
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Cells responsible for collagen synthesis?
- Fibro
- Chondro
- Osteo
- Cemento
- Odonto
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Most common form of collagen?
Type 1
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Type 1 found in?
Skin, bone, tendon, dentin, pulp
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Collagen fibers are made up of _____
fibrils in characteristic striations every 67nm, hallmark for ID
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What differentiates the types of collagen?
Combinations of linkages of the polypeptide chains
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Two main classes of collagen?
- Fibrillar (Type I, III, V, XI)
- Non-fibrillar
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Collagen II (NF) found in_______
mostly cartilage, not in pulp
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Type III collagen co-distributes with _____
Type I
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Type III collagen found where?
Reticular fibers (fine fibers) mainly used in embryogenesis, inflammation, and wound healing
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Type IV and VII present
in basement membranes
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Type V collagen present in
unmineralized tissues
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Type VI collagen is found
distributed in body as interfibrillar filaments
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Amount of collagen in dried pulp in PM? 3rd molar?
25.7% vs 31.9%
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Type III collagen in pulp, percent and where?
42.6%, forms thinner fibrils, cell-free and cell-rich zones
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Is type I collagen exclusive to pulp?
NO, but it is definitely to dentin.
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What types of collagen can be found in predentin?
I, III, V
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Korff fibers were originally described as
argyrophilic fibers
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Korff fibers pass ______ between the odontoblasts entering the ______.
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Korff fibers particularly evident during
early dentinogenesis, involved with mantle dentin and odontoblast differentiation
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Korff fibers mainly composed of which collagens
I, III
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What other collagens have been observed in the pulp?
- V, VI
- form dense meshwork of thin microfibrils
- VI found between odontoblasts toward predentin suggesting comp of Korff
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Type IV collagen forms the
basement membranes of pulpal blood vessels
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Describe how CaOH works to induce collagen formation.
- First produces necrotic zone bc of high pH
- fibroblast-like cells, inflammatory cells migrate to site
- formation of new collagen close to necrotic zone with cellular inclusions
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GAGs are ____, ______ polymers of repeating __________ units.
- long
- unbranched
- disaccharide
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Four main types of GAGs?
- Chondroitin sulfate/dermatan sulfate
- heparan sulfate/heparin
- keratan sulfate
- hyaluronic acid
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The 3D structure of proteoglycans can be likened to
an interdental brush, the metal is the protein and the bristles are the GAGs
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Why are proteoglycans so hydrophilic?
carboxyl, hydroxyl, sulfated hexosamines
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The long GAG chains allow for storage of?
Water, lots of it, form a shock absorbing gel that protects connective tissue
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Since they are cationic, proteoglycans attract
matrix proteins and GFs like TGF-β, act as a bioactive molecule pool
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What is syndecan?
Proteoglycan on cell membrane, binds collagen, fibronectin, tenascin. Cell-surface receptors that connects matrix molecules to the cytoskeleton
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Name the proteoglycans found in consistently in pulp?
- Chondroitin sulfate
- dermatan sulfate
- hyaluronic acid
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Dentins main proteoglycan is
chondroitiin sulfate
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Chondroitin sulfate plays what role in dentinigenesis?
strong capacity to bind calcium and may maintain levels of calcium-phosphate during mineralization
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How to proteoglycans mechanically stop bacteria?
Viscosity
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How do bacteria counter PGs viscosity?
Streptococci produce hyaluronidase (hydrolyzes GAGs)
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Fibronectin a glycoprotein exists as the three in pulp:
- 1. plasma protein
- 2. protein attaches to cells
- 3. insoluble fibrils form ECM
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Fibronectin acts a mediator for ______ and ______ adhesion and thus has major effect on the ____________, ____________, and _____________ of cells
- cell-cell
- cell-matrix
- proliferation
- differentiation
- organization
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Fibronectin is immunolocalized in the odontoblastic layer where it forms _______ fibers that pass from _____ into _______ parallel to longaxis of OD.
- corkscrew
- pulp
- predentin
- (which suggests constituent of Korff fibers)
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Odontoblasts and fibronectin?
morphology controlled by
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Relations of OD cell bodies predentin and fibronectin?
FN contributes to tight seal here
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FN implicated in reparative dentinogenesis, how?
Immunolocalized during CaOH capping, allows for diff of OD and migration
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Osteonectin is a __________ protein that has affinity for ______ and _________ and promotes the deposition of _______ _______ mineral onto ________.
- non-collagenous
- calcium
- hydroxyapatite
- calcium phosphate
- collagen
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What non-collagenous proteins are found in the pulp?
- Fibronectin
- Osteonectin
- Bone sialoprotein
- Osteopontin
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Odontoblast nucleus contains up to how many nucleoli?
4
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Diameter of odontoblast process?
3-4μm
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Odontoblast processes do/do not extend to the outer dentin
do not, except during early tooth development
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What kind of junctions keep odontoblasts together?
desmosome-like jxn
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What there junctions are common to odontoblasts?
desmosome-like and gap jxns and tight
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Which junction is involved in cell adhesion for the odontoblast?
desmosome
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which junction is involved in pathways for intercellular ion transfer, between odontoblasts?
gap jxns
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What jxn exists where the cell body and process interface is close to another odontoblast?
Tight jxn, prevent passage of materials between cells
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Why is it unclear if the tight junctions encircle the whole odontoblast?
small nerve fibers and collagen fibers pass through interodontoblastic space, known as macular or "leaky"
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What molecule do odontoblasts present making them defense cells?
TLRs (Toll Like Receptors)
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What bioactive substances do odontoblasts secrete?
- chemokines
- TGF-β (OD are main source in pulden complex)
- MMPs
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What non-col proteins do OD synthesize?
- bone sialoprotein
- dentin sialoprotein
- dentin phosphoprotein
- dentin matrix protein 1
- osteoclacin
- osteonectin
- osteopontin
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What specific MMPs do OD synthesize?
- MMP-8 (collagenase 2)
- MMP-2,9 (gelatinases)
- MMP-20 (enamelysin)
- MMP-14
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What are thr findings that show OD are involved in innate immunity?
- 1. express TLRs
- 2. produce chemokines and express chemokine receptors
- 3. produce antimicrobial peptides such as β-defensins
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TLR-2 recognizes products of
gram-positive bacteria (lipoteichoic acid)
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TLR-4 recognizes
lipopolysaccharides prod by gram - bacteria
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Activation of TLR by microbial ligands causes
prod of cytokines, chemokines, defensins
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Which dentin specific protein marks the odontoblast phenotype?
dentin sialoprotein
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What do fibroblasts produce?
- Type 1, 3 collagen
- Fibronectin
- Proteoglycans
- Osteonectin
- Osteopontin
- Bone Sialoprotein
- TGF-β1
- BMP-2,4
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Fibroblasts secrete MMPs, which one of these has limited expression in other normal adult tissue?
MMP-13 (collagenase-3)
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What are the antibody secreting cells?
B-lymphocytes, humoral immunity
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What is the main job of T cells?
cause lysis of other cells that carry foreign antigens
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Two types of T cells?
CD4 helper cells, humoral and cell-mediated immunity
CD8, cytotoxic, cell mediated
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Match MHC to T cell?
MHC Class I binds to CD8
MHC Class II binds to CD4
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MHC Class I or II is also termed
HLA, human leukocyte antigen
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Expression of MHC Class I and Class II, which cells?
Class I is expressed on almost all cells
Class II is expressed on dendritic cells and B lymphocytes (macrophages can be induce)
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Where are T lymphocytes scattered in the pulp proper?
Along the blood vessels
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Numbers of CD8 to CD4?
CD8 outnumbers CD4
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Which lymphocytes are rarely found in the pulp?
B lymphocytes and plasma cells
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Macrophage function?
phagocytosis of foreign particles, self-tissues, injured or dead cells (bone marrow derived cell)
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Where are macrophages found in pulp?
Everywhere but rich in perivascular area of inner pulp
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Where are dendritic cells derived?
hematopoietically derived
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Characteristics of dendritic cells (5)
- 1. dendritic morphology
- 2. Class II MHC
- 3. high motility
- 4. limited phagocyctic
- 5. potent capacity for antigen presentation
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Where do dendritic cells mature and what tissues do they populate?
- Bone marrow
- nonlymphoid tissues
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Dendritic cells express what factor also seen in cells of the dermis?
coagulation factor XIIIa
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Dendritic cells of pulp reside
in periphery of the pulp, sometimes compete for space with odontoblasts evening expressing their processes into the tubules
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Following ingestion of antigen what two ways may dendritic cells act?
- 1. migrate to regional lymph nodes to present antigen to naive T lymphocytes to start primary immune response
- 2. locally present antigens to patrolling T lymphocytes (secondary immune response)
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The two types of cells termed pulpal dendritic cells
Dendritic cells and macrophages
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The intensity of inflammatory and immunologice responses correspond to the ______ and ______ of _______ and _________ processes of dentin that influence dentin permeability
- status
- quality
- reactive
- reparative
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______ et al have demonstrated that the accumulation of _______ cells remains evident even _ months after caries removal with the aid of a caries detector dye and resin restoration with resin.
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What is the major function of connective tissue?
- provide a matrix that binds cells and organs
- gives support to the body
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What is ground substance composed of?
- Proteoglycan (GAGs and protein)
- Fibronectin (cell adhesive)
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Cell free zone is also known as the zone of _____
Weil
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