Microanatomy Test 4

aknight1302's version from 2015-11-17 16:34


Question Answer
Stomatodeumcavity between Frontal Prominence and Cardiac Bulge (embryo development of mouth) 25th day
First Pharyngeal Arch differentiates intomaxillary and mandibular processes (embryo development of mouth)
Epithelium derived component of toothEnamel
Neural Crest, origin of all tooth structures EXCEPT ____?enamel
Enfolding from epithelium into ectomesenchyme that will develop into tooth budsDental Laminae (max and man)
What is between the ectomesenchyme and epithelium of the Dental Lamina?Basement Membrane
What starts developing first? enamel or dentinDentin starts first, (though the pre-odontoblasts are stimulated to differentiate and then build dentin by the pre-ameloblasts... pre-ameloblasts don't start creating enamel layer until there is dentin to build it against)... basement membrane is still present initially
Layers of the Enamel OrganInternal Enamel Epithelium (IEE), External Enamel Epithelium (EEE), Stellate Reticulum, stratum intermedum
What LAYER of the ENAMEL ORGAN adjoins the DENTAL PAPILLA?Internal Enamel Epithelium (enamel genesis from this layer)
What LAYER of the ENAMEL ORGAN adjoins the DENTAL FOLLICLE?External Enamel Epithelium (EEE)
What LAYERS surround the STELLATE RETICULUM?IEE and EEE (Stellate Reticulum is middle layer of the ENAMEL ORGAN, which is of epithelial origin)
What ectomesenchymal structure surrounds and encapsulates the enamel organ?Dental Follicle
What ectomesenchymal structure invaginates the enamel organ?Dental Papilla
During what stage is the ENAMEL KNOT visible? and where?cap stage, disappears by bell stage... found in the stellate reticulum adjoining the center of the IEE
Ectomesenchymal tissue has its origins in the ____ ____Neural Crest
What tooth structure(s) is/are derived from the ENAMEL ORGANenamel
What tooth structure(s) is/are derived from the DENTAL PAPILLAdentin and pulp
What tooth structure(s) is/are derived from the DENTAL FOLLICLE (SAC)Cementum, Periodontal Ligament, Alveolar Bone
Cervical Looparea where IEE and EEE meet, BECOMES CEJ and is boundary of crown formation, appear in the bell stage
What is the cell type of Preameloblasts?"low" columnar, w/ central nuclei
What induces the differentiation of Preameloblasts into Secretory Ameloblasts?presence of Mineralized Dentin across basement membrane (specifically, Mantle Dentin is the Dentin that is deposited against the basement membrane... triggering the differentiation of PreAmeloblasts into Secretory Ameloblasts)
Where are HYAP crystals formed in enamel formation? (structure, cell, tissue layer)in the Tomes' Processes of Secretory Ameloblasts in the Internal Enamel Epithelium
What is orientation of Distal Tomes' Process product to the cell producing it?parallel (or an extension of the same line), this forms Rod Enamel and fills the pits made by walls of Inter-rod Enamel
What is orientation of Proximal Tomes' Process product to the cell producing it?perpendicular, this forms Inter-Rod Enamel and creates walls for formation of Rod Enamel
What IS the product of Secretory Ameloblasts?ENAMEL, (specifically Needle-like HYAP crystals sheathed in enamel proteins) (proteins digested and crystals grown to become Enamel as we know it)
How many Ameloblasts make the transition from SECRETORY to MATURATIVE?about 50% undergo APOPTOSIS, others become Maturative
What is the function of Maturative Ameloblasts?Enamel Hardening
What are the 2 types of Maturative Ameloblasts?Ruffle-bordered and Smooth-bordered
What do Ruffle-bordered Ameloblasts do?secrete calcium ions for crystal growth, (enamel hardening), Ruffle-bordered are Maturative Ameloblasts
What do Smooth-bordered Ameloblasts do?uptake digested polypeptides (cleared enamel matrix/crystal sheaths... make room for crystal growth), Smooth Bordered are Maturative Ameloblasts
What does the Enamel Organ become after Enamel formation is complete?Reduced Enamel Epithelium
What is the difference between Pre-Dentin and Dentin?Pre-Dentin is newer (just formed) and UNMINERALIZED, Dentin is MINERALIZED and used to be pre-dentin
Fusion of IEE and EEE happens where, when and forms what?happens at cervical loop, coinciding with tooth eruption, forms HERTWIG's EPITHELIAL ROOTH SHEATH
lifecycle of Hertwig's Epithelial Root Sheath1. at tooth eruption FORM, comprised of IEE and EEE 2. communicate with Odontoblasts to differentiate into RADICULAR odontoblasts (form root dentin, NOT crown dentin) 3. Break Down (Herwtig's Root sheath has done its job and now recedes) (goodbye Hertwig)
function of Hertwig's Epithelial Root Sheathcause differentiation of pre-odontoblasts --> radicular odontoblasts (end crown formation, start root formation)
What induces the differentiation of Cementoblasts?the breakdown of Hertwig's Root Sheath and presence of Radicular Dentin
What factors influence Crown Pattern Differentiation?Homeobox Genes
Which mineralized tissue in the tooth has the greatest hardness?enamel (this is because of its rigid and highly inorganic composition HYAP)(it is also more brittle, or and has less tensile strength)
Which mineralized tissue in the crown of the tooth has the greatest tensile strength (acts as a shock absorber)?Dentin (because it's greater protein makeup relative to enamel, it has greater tensile strength and is less brittle.)
Morphodifferentiation, (bell stage)Crown of tooth determines its final shape (MORPHODIFFERENTIATION of the tooth)
Histodifferentiation, (bell stage)differentiation to Ameloblasts and Odontoblasts (IEE and Dental Papilla respectively)
At what stage does the Dental Lamina "disappear"?Bell stage
mnemonic for distal vs. proximal tomes process and their products?DRIP. Distal-Rod Interrod-Proximal (dpTP, ppTP)
What cells are found in a single layer lining the pulp cavity?odontoblasts


Question Answer
Why are Rods "more susceptible" than inter-rods to acid etching?THEY'RE NOT... it all depends on the orientation... (which can be different depending on the location of restoration)
Unlike bone, dentin, and cementum, ENAMEL is a mineralized _____ tissue (tissue origin type)mineralized EPITHELIAL tissue
by-weight composition of enamel96% inorganic, 1% organic, 3% water
what are the two amelogenic proteins found in enamel?Tyrosine-Rich Amelogenic Protein (TRAP) & Lysine-Rich Amelogenin Protein (LRAP)
What non amelogenic proteins are found in enamel?enamelin, amelin, & tuftelin
Incremental Linescan be seen from longitudinal section, often formed during period of sickness, due to sensitivity of ameloblasts
Where would you find APRISMATIC enamel?at the DEJ and at the outer enamel surface of erupted tooth (innermost and outermost, newest and oldest)
Where are ENAMEL SPINDLES found and what are they?Enamel spindles are found at the DEJ, they are remnants of Odontoblastic processes that are trapped in early amelogenesis
Stages of Ameloblast lifecycleMorphogenetic (undifferentiated) (central nuclei in IEE), Histodifferentiation (IEE signals differentiation in preodontoblasts, then wait for initial dentin to move to next phase) (polar nuclei) Secretory (initiated in response to initial dentin, Tomes' Processes do they thing and build enamel of a crown happens) Maturative (enamel hardening, cells alter between smooth bordered and ruffle bordered) Protective ("protect" and involved in tooth eruption, REE fuses into oral mucosa)
What factors are secreted by Preameloblasts to induce differentiation of undifferentiated prodontoblastic cells?TGF-(B1), BMP-2, IGF
What part of the Tomes' Process is "missing" during initial enamel secretion?the Distal portion of Tomes Process (dpTP), hence no rod/interrod of aprismatic, initial enamel
What is the 2nd level of enamel organization?rod-groups criss-crossing (provide added structural support)
What is the 1st level of enamel organization?rod/interrod organization (key hole)
Enamel HARDENING is done by ____ Ameloblasts.... increasing ___ and breaking down and absorbing ____Maturative, Crystal size (mineralization)(through CRYSTAL GROWTH, not new crystals), matrix proteins
True or False: Enamel hardening is achieved through the deposition of new HYAP crystalsFALSE (hardening is achieve through the GROWTH of pre-existing crystals)
Where is the HARDEST enamel found and why is it harder?TOOTH SUFACE (final enamel) is harder because of higher mineral content (more hardening by maturative ameloblasts)
What are the layers of the Reduced Enamel Epithelium?IEE, OEE, Stratum Intermediate, Stratum Reticulum (same as enamel organ)
How many Ameloblasts from a single enamel rod?1 (rod is directional and product of dpTP of an ameloblast)
How many Ameloblasts form interrod enamel around a single rod?4 (inter-rod is a product of the ppTP and neighboring ameloblasts secrete up against each other)
What is the unmineralized matrix protein precursor of enamel?(TRICK QUESTION) There is no unmineralized matrix protein precursor of enamel
What is the most abundant type of enamel protein? (in completed teeth)Amelogenins (90%)
Which enamel proteins prevent crystal fusion?Amelogenins
Which enamel proteins are found more in LATER (forming process) enamel?Amelogenins
Which enamel proteins "stimulate and regulate crystal growth"?Non-amelogenins
Which enamel proteins are found more in EARLY (forming process) enamel?Non-amelogenins
Knockout of which proteins lead to ENAMEL HYPOPLASIA?(formation of enamel, but very weak)AmeloGENins
Knockout of which proteins lead to ENAMEL AGENESIS? (no enamel formation)AmeloBLASTins

Dentin (cont in pt 2)

Question Answer
Where do you find the oldest Dentin?at the DEJ
Where do you find Pre-dentin?against the PULP... or at Pulp-Dentin Junction (b/c this is where new dentin is being formed)
Direction of Dentin, old to newfrom DEJ to Pulp
Direction of Dentin, new to oldfrom Pulp to DEJ
Are Dentin Tubules wider toward the pulp, or toward the DEJ?Wider toward the pulp, narrower toward the DEJ
Are Dentin Tubules narrower toward the pulp or toward the DEJ?Narrower toward DEJ, Wider toward Pulp
Dentin Tubules branch and interconnect where?area near DEJ... believed to involve communication? (more branching in root, less in crown)
Peritubular (INTRAtubular) dentindentin that makes WALLS of tubules... more mineralized, denser than dentin between tubules
INTERtubular Dentindentin between tubules. and not adjoining the tubules. LESS DENSE, LESS MINERALIZED
Mantle Dentininitial deposition @ DEJ (first dentin formed..., first we'll hit with bur when prepping)
Primary Dentin (formation and where)?from start until functional loading (against DEJ) (same as Mantle Dentin)
Secondary Dentinformed under functional loading (and after root completion, they coincide) (formed throughout life)
Tertiary Dentincreated in response to trauma or caries
Predentinunmineralized dentin matrix, being formed, adjoining pulp
Which forms faster, 2-ary or primary Dentin?primary dentin forms faster, as functional load is added, formation slows
Tubules alter their orientation at what formative step?shift from primary to secondary dentin
What type of dentin forms in response to caries or trauma?TERTIARY Dentin (may engulf odontoblasts) LOCALIZED to irritated area
Why is it harder for bacteria to go through TERTIARY DENTIN?because tubules become narrower (if present) or disconnect... matrix MAY or MAY NOT have tubules (like blocking a door in a horror movie)
What type of cells make Tertiary Dentin?Odontoblast-LIKE cells (generated from stem cells in response to caries/trauma) (like blocking a door in horror movie)
These cells do not divide, also they create mineralized product by first laying down a collagen matrix and then mineralizing...Odontoblasts
Dead Tracts (what are they?)(more/less susceptible to bacterial invasion?)left behind dentin tubules after death of ODONTOBLASTS, walled off by tertiary dentin, dead tracts are more susceptible to bacterial invasion
Sclerotic Dentinminerals deposited in Dentin Tubules...
Dentin that has a "glassy appearance"Sclerotic Dentin, Dentin tubules filled w/ minerals... harder and more brittle
Age associated changes in Dentinsclerotic toward pulp, dentin becomes chalky (compromises the mechanical properties of dentin) this is why you can more easily break tooth as you get old
What type of dentin is deposited in response to trauma or infection?TERTIARY dentin
What FIBERS make up the majority of PRE-DENTIN?Coll fibers (perpendicular to odontoblasts)
What FIBERS are larger and run PARALLEL to ODONTOBLASTS?von Korff's fibers
What cell in the tooth is most like Osteocytes, having extensive branching connections between cells?Odontoblasts
What are Tomes' Fibers?extensions of odontoblasts within dentin tubules, part of cell body, connect to DEJ (branching near DEJ w/ extensive connections between cells)
What is the mineral composition of PRE-DENTINUNMINERALIZED
Most mineralization of dentin is done by ____ mineralizationGLOBULAR (secretory vesicles)
Rank Enamel, Bone, and Dentin in terms of hardnessEnamel > Dentin > Bone



Microanatomy Test 4 pt. 2