Oral Histology Exam 2
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Primary bone in the diaphysis of long bones
Bone subject to bending, torsional, and compressive forces
Bone subject to primarily compression forces
Greatest strength of which bone is along long axis
Cortical bone AND Lamellar bone
Periosteum is very important for
collagen for bone
Proteoglycans and Hyaluonan are important for
- Space filling
- Decorin, biglycan, and versican
Glycosylated proteins include:
- Alkaline phosphatase - regulate P and Ca dynamics
- Osteonectin - bridge between collagen and hydroxyapatite
Glycosylated proteins with cell-attachment properties include
- Fibronectin, vitronecting, and bone sialoprotein
- Important for RGD domains, bind integrins and influence cell-ECM interaction
- Seal off sealing zone in osteoclast sites
Gamma-carboxylated (Gla) containing proteins
- Matrix Gla protein, osteocalcin
- Regulators of mineralization
Endochondral ossification occurs in conjunction with
What induces transcription factors that mediate commitment of early progenitor cells toward a osteoblast phenotype?
- Alkaline phosphatase
- Type I collagen
- Indirectly responsible for mineralization
Osteoblasts are derived from
- Mesenchymal stem cells during development
- Bone marrow stem cells postnatally
Basophilic b/c they have abundant RER
- Indirectly responsible for mineralization
- Indirectly regulate calcium homeostasis
- Regulate differentiation and activity of osteoclasts
- Secretion of mixture of bone matrix proteins
Most abundant cells in bone are
Terminally differentiated osteoblasts
Osteoclasts produce _______ to resorb bone
TRAP (Tartrate-resistance acid phosphatase)
Osteoclasts are found in
Osteoclasts are derived from
- Large multinucleated cells -- fusion of monocytes and macrophages
- From pluripotent hematopoietic stem cells in bone marrow that give rise to monocytes and macrophages
RANK essential for ______function
Osteoclast differentiation and activation
Bone matrix is degraded by
Enzyme acid phosphatase and cathepsin B
Runx2 is the locus for
Runx2 is ______ regulator of osterix
Bone remodeling takes place:
on bone surfaces like periosteal, endosteal, haversian canals, and trabecular sufaces
Bone remodeling cycle takes 3-4 months.
% cortical bone remodeled/yr
5 Phases of Remodeling
- Activation of osteoclasts
- Resorption of bone
- Reversal phase
- Formation of bone
Bone ____ doesn't depend on alkaline phosphatase but __________ do.
- Propagation and ECM mineralization
Where is cementum thickest?
Apex and interradicular area of multirooted teeth
Lines produced by continuous but phasic deposition of cementum called
Incremental or resting lines
2 unique cementum molecules
- Cementum attachment protein (CAP)
Cementoblasts are derived from
Hyaline layer of Hopwell-Smith is also called:
- Intermediate cementum
- 1st layer of cementum that is formed by inner cells of HERS and is deposited on the roots surface
- Deposition occurs before HERS disintegrates
- Situated between the granular layer of Tomes and secondary cementum that is formed by cementoblasts
Cementum is _____ permeable that other dental tissues
Type of cementum covering root adjacent to dentin
Cellular cementum can be found
in the apical area and overlying acellular cementum
- Border with dentin is not clearly demarcated
- Rate of development is slow
- Incremental lines are close together
- Precementum layer virtually absent
- Border with dentin clearly demarcated
- Rate of development fast
- Incremental lines are far apart
- Precementum layer present
The organic matrix of cementum is derived from 2 sources:
- PDL (Sharpey's fibers)
Extrinsic fibers (cementum) are:
- Derived from PDL
- In the same direction as the PDL
Intrinsic fibers (cementum) are:
- Derived from cementoblasts
- Parallel to root surface
Acellular Extrinsic Fiber Cementum (AEFC)
- Primary cementum
- Located in cervical 1/2 of root
- Constitutes the bulk of cementum
- Collagen fibers from Sharpey's but ground substance from cementoblasts
- Principle tissue of attachment
- Function in anchoring the tooth
- Well mineralized
Cellular Intrinsic Fiber Cementum (CIFC)
- Secondary cementum
- Starts forming after tooth is in occlusion
- Majority of fibers organized parallel to root surface
- Very minor role in attachment
- Seen in middle to apical 1/3 of root and in interradicular area
Secondary Cellular Mixed Cementum
- Both intrinsic and extrinsic
- Bulk of secondary cementum
- Apical portion and interradicular
- Intrinsic fibers uniformly mineralized but extrinsic fibers are variably mineralized with some central unmineralized cores
Acellular Afibrillar Cementum
- Limited to enamel surface
- Close to CEJ
- Lacks collagen so no role in attachment
CEJ - OMG Rule
- Overlaps enamel - 60%
- Meets enamel - 30%
- Gap between cementum and enamel - 10%
What happens as cementum ages
- Smooth surface becomes irregular due to calcification of ligament fiber bundles where they are attached to cementum
- Continues deposition with age in apical area (good b/c maintains tooth length. Bad: obstructs foramen)
- Cementum resorption
Cementum resorption generates
Reversal lines because it is active for a period of time and then stops for cementum deposition
Cementicles are found in:
What causes resorption of dentin and cementum
Result of loss of cementum is
- Loss of attachment
- Once there is reparative cementum deposition the attachment is restored
Mandible and maxillay form a groove that is opened toward the surface of the oral cavity (future alveolar process) when?
During end of 2nd month of fetal life
Alveolar process starts to develop
Strictly during tooth erupting
Structure of alveolar process
- Outer cortical plates
- Inner spongiosa
- Bone lining alveolus
Alveolar bone proper contains:
- Perforating fibers from PDL (Sharpey's fibers)
- Just compact bone
Alveolar bone called lamina dura because:
It appears more radiodense than surrounding supporting bone in xrays
2 other names for alveolar bone are
Alveolar bone is called bundle bone because:
- It is perforated by many foramina that transmit nerves and vessels (cribriform plate)
- Because alveolar process is regularly penetrated by collagen fiber bundles
Lining of alveolus becomes smoother or rougher as one ages?
PDL is thinnest:
in the middle portion of the root
PDL width increases or decreases with age:
When does PDL form and from what?
From dental follicle shortly after root development begins
What happens to the PDL as tooth erupts?
Change in orientation of fibers
Functions of PDL
- Shock absorber
- Tooth support
- Sensory receptor - necessary for proper positioning of the jaw
Most abundant cell in PDL
Fibroblasts (make collagen)
Osteoclasts in PDL are
critical for periodontal disease and tooth movement
Cementoclasts are found in PDL ONLY in
Types of collagen in PDL
1, 3, 12
The average diameter of individual collagen fibers in PDL are _____ than other areas of the body due to the shorter half life of PDL fibers
3 types of PDL fibers
- Collagen fibers
- Oxytalan fibers - perpendicular to teeth and adjacent to capillaries, variant of elastic fibers
- Eluanin - variant of elastic fibers
Fibers of dentoalveolar group of PDL
- Alveolar crest group
- Horizontal group
- Oblique group (most numerous)
- Interradicular group
- Sharpeys fibers - at each end, fibers embedded in bone and cementum
Fibers of Gingival group of PDL
- Dentogingival (most numerous) - cementum to gingiva
- Alveologingival - alveolar bone to gingiva
- Circular - not attached to tooth, around neck of tooth
- Dentoperiosteal - runs apically from cementum over outer cortical plate to alveolar process or muscle or floor of mouth
- Transseptal - from cementum to cementum, over alveolar crest
What is the function of oxytalan fibers?
To regulate vascular flow in relation to tooth function
Oxytalan fibers are most numerous in
Blood supply to teeth is higher in posterior or anterior?
Mandibular or maxillary?
Oxytalan fibers are associated with
Which tooth region contains more nerve endings? (Except maxillary incisors)
What is the major GAG in ground substance of PDL?
Ground substance is a major constituent of
How much water is in ground substance
What happens when function of ground substance is increased vs. decreased?
- Increased = PDL increased in size and fiber thickness
- Decreased = PDL narrows and fiber bundles decrease in # and thickness
- Decrease happens due to increased cementum deposition
Phases of Tooth Eruption
- Preeruptive - from initiation and formation to initiation of root formation
- Eruptive - from initiation of root formation to occlusal contact
- Posteruptive - after occlusal contact
Stages of eruptive phase
- Root formation
- Occlusal contact
Why do developing crowns move constantly in jaws during preeruptive phase?
To place teeth in position for eruptive movement.
What are the two types of movement during the preeruptive phase?
- Total bodily movement
- Movement where one part remains fixed while rest continues to grow leading to a change in the center of the tooth germ
Rates of tooth eruption depend on phase of movement. Which is faster, intraosseous phase or extraosseous phase?
- Extraosseus - 75micrometers /day
- Intraosseous is only 1-10
Mechanisms of Eruptive Tooth Movement
- Root Formation
- Bone Remodeling
- Dental Follicle
Reasons for Post eruptive tooth movement
- To accomodate growing jaws
- To compensate for continued occlusal wear (cementum growth at root apex)
- To accomodate interproximal wear - mesial drift (controlled by shortening of transseptal fibers and more)
Mesial drift controlled by
- Shortening of transseptal fibers
- Adaptability of bone tissue (side of pressure on PDL causes bone resorption, pull on fibers causes bone formation)
- Anterior compartment of occlusal force due to mesial inclination
- Pressure from soft tissues like buccal mucosa and tongue
Active eruption compensates for
incisal and occlusal wear
Passive eruption due to
gradual recession of the gingiva and underlying alveolar bone
2 phases of hard tissue resorption
- Extracellular phase
- Intracellular phase
Functions of oral mucosa
- Thermal regulation (in dogs not humans)
3 types of oral mucosa
- Masticatory (keratinized, 25%)
- Lining (non keratinized, 60%)
- Specialized (15%)
Factors affecting color of oral mucosa
- Concentration and state of dilation
- Thickness of epithelium
- Degree of keratinization
- Amount of melanin pigmentation
Sebaceous glands in oral cavity, predominantly in upper lip, buccal mucosa, and alveolar mucosa
Interface between epithelium and CT of oral mucosa is made of a structureless layer called
Basement membrane interface of oral mucosa is irregular and composed of downward projections called ______ and upward projections called _______.
- Rete ridges/pegs
- Connective tissue papillae
Junction between ___ and lamina propria is more obvious than that between lamina propria and submucosa.
- loose fat and glandular tissue
- Provides flexibility
The gingiva and hard palate do not have which layer of tissue?
- Tissue instead called mucoperiosteum
Which tissue turns over faster? keratinized or nonkeratinized?
Components of lining mucosa:
- Stratum basale - cuboidal cells, progenitor cells that divide and provide new cells by mitotic division that migrate to the surface
- Stratum spinosum/intermedium - oval, bulk of epithelium
- Stratum superficiale - flat, small oval nuclei, continuously shed
What is eleidin?
Transparent, semi-fluid substance present in stratum lucidum of skin epithelium - helps make lips red
Masticatory mucosa layers
- Stratum basale and spongiosum - same as nonkeratinized
- Stratum granulosum - contains keratohyaline granules
- Stratum corneum - thin, flat nonnucleated cells which are filled with keratin
Parakeratinized epithelium ___ nuclei, whereas orthokeratinized epithelium ______ their nuclei.
Rete pegs are what shape in keratinized epithelium
long and slender
What type of epithelium is on gingiva
Thick orthokeratinized or parakeratinized epithelium
What is stippling in gingiva?
In healthy attached gingiva, appears as small pits in epithelium - due to deep rete pegs
Free gingiva is/is not stippled?
Attached gingiva is/is not stippled?
Dentogingival junction is important because
it's where oral mucosa meets surface of tooth and is a weak area in the oral mucosa which is otherwise continuous
Which type of epithelium lines the wall of the gingival sulcus?
Nonkeratinized stratified squamous epithelium
Junctional epithelium is derived from:
Reduced enamel of the tooth germ
How is junctional epithelium attached?
- To enamel by internal basal lamina
- To CT by external basal lamina
- Hemidesmosomes are present in both basal laminas
What readily regenerates from the sulcular epithelium or oral epithelium if its damaged or surgically extracted?
What is present in the CT of gingiva that is different from normal oral mucosa?
What is Col?
- A depression
- Col epithelium is identical to junctional epithelium and has same origin and is also continuously replaced by cell division
Hard palate epithelium is:
Orthokeratinized (some parakeratinized)
Ducts of von Ebner empty into
Which type of specialized mucosa does not contain taste buds?
Which type of specialized mucosa is most numerous?
Nerves for taste buds arise from ________ in anterior tongue and ________ in posterior tongue
- Chorda tympani (VII)
Epiglottis and larynx innervated by
Taste buds made up of 4 types of cells (Types 1-4), Distribution is:
- Type 1 dark cell - 60%
- Type 2 light cells - 30%
- Type 3 - 7%
- Type 4 - 3% (basal cells)
Locations of taste sensations
- Sweet and salty - anterior tongue
- Sour - lateral tongue
- Bitter - region of circumvallate and soft palate
Epithelial cell-cell contact is made through desmosomes. In the oral cavity is appears discoid and is called:
Pemphigus vulgaris is what?
Autoimmune disorder that involves blistering of mucous membranes
3 Major nonkeratinocytes in oral epithelium that are clear with a halo around nuclei:
1 that isnt clear.
- Langerhans cells - found on stratum spinosum, antigen trapping, dendritic, no desmosomes/tonofilaments
- Merkel cell - in basal cell layer (mostly in gingiva), touch receptors, non dendritic, sparse desmosomes/tonofilaments
- Melanocytes - basal cells, melanin producing, dendritic
Lymphocytes and leukocytes aren't clear cells, associated with inflammatory response
Layers of lamina propria in oral mucosa:
- Superficial papillary layer (associated with rete ridges)
- Deeper reticular layer (between papillary and deeper structures)
Parotid gland is a __ gland. Which duct?
- Stensen's duct
- Largest salivary gland
- 25% of total saliva
- Anterior floor of mouth
- 5% of total saliva
- Viscous saliva
- Ducts of Rivinus; duct of Bartholin
- Mixed sero-mucous
- 60% of total saliva
- More mucinous
- Wharton's duct
Glands of Blandin-Nuhn are found ________. Glands of Weber are found ________.
- Ventral tongue
- Posterior lateral tongue
Embryologic origin of parotid is_________.
Embryologic origin of sublingual and submandibular glands is ____________.
Salivary glands form by process called
Zymogen granules are precursors to
2 stages of saliva
- Primary saliva - isotonic, contains mostly organic component and water
- Modified saliva - hypotonic, striated and terminal ducts, reabsorption and secretion of electrolytes
NE via A-adrenergic receptors and substance P can activate what pathway in mouth?
Ca2+ phospholipid pathway
Bicarb is transported into lumen via
Apical Cl- channels
Excretory portion of salivary ductal system lies
in CT septa between lobules
Path of saliva from duct:
Acinar cells --> intercalated ducts --> striated ducts --> excretory ducts
Which are larger, striated or intercalated ducts?
Striated ducts secrete a hypotonic solution with what ion balances?
What is the role of hormones on saliva?
Modify saliva content but can't initiate salivary flow
Events of repair/regeneration:
- Disruption of mucosa
- Hemorrhage and fibrin formation
- Vasoconstriction for protection
- Hemostasis (clotting)
- Scaffold for repair
- Neutrophils - 1st response, kill bacteria and everything else
- Macrophages - 2nd, chemotaxis, release of growth factors, cytokines bring lymphocytes
- Mast cells - source of proinflammatory mediators
What protein gets secreted in repair process?
Why is it difficult for tissue to heal in periodontal disease?
- Because of the loss of connective tissue - MAIN PROBLEM
- causes migration of junctional epithelium
Types of joints
Synovial, sliding, ginglymoid joint
Embryology of TMJ
- Primary - Meckels cartilage
- Secondary - starts developing at 3 months gestation - 2 blastemas -temporal and condylar (temporal first so condylar grows towards temporal)
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