12.2 - Lab + Lecture Notes Flashcards
Vermillion Border
= the transition zone in the lip between the SSK of the skin and the SSNK of the oral cavity
Orbicularis Ovis
= skeletal muscle in the lip
- lies deep to the mucosa
- encircles the lip to form the 1st sphincter of the GI tract
Filiform Papilla
- folds in tongue where the tufts of keratin extend perpendicularly away from epithelial surface
Fungiform Papilla
- interspersed among the filiform papilla
- roughly the same size as the filiform papilla
- have shape of little mushrooms
- contain taste buds
Circumvallate (Vallate) Papilla
- present only towards the back of the tongue
- only 8-12 per person
- also mushroom shaped (like fungiform papilla)
- much larger than other papilla
- are raised from the tongue surface
- contain taste buds on the lateral surfaces facing the moat (where von Ebner’s glands empty their serous saliva)
Describe Tooth development in 4th month in two bullet points
- deciduous (baby teeth) begin to acquire enamel
- tooth germs of permanent teeth begin to form
Describe the role of ectomesenchymal cells in tooth development
- neural crest cells separate from ectodermal epithelium and migrate laterally within fetal mesodermal tissue
- they take residence as ectomesenchymal cells under the future oral ectoderm
- there they induce the condensation of mesenchymal tissue + the formation of the dental lamina
Dental lamina
= invagination of oral ectoderm
- occuring in 2 u-shaped areas within the oral cavity
- places where you would expect teeth to form
- these invaginations give the name of this stage = BUD STAGE
Cap Stage - why is it named this (include an important organ)
= named for appearance of general shape of invaginated dental lamina –> forms enamel organ
Enamel Organ
- roughly spherical structure in the mesenchymal tissue near the futureoral epithelium
- connected by thread of previous dental lamina to oral epithelium
- contains an Inner Enamel Epithelium = flattened portion farthest from the oral cavity
- Outer enamel epithelium = the rest of the sphere
- inside is the stellate reticulum
Stellate reticulum
- inside of enamel organ
- composed of highly hydrated GAG-filled CT-like structure
- resident cells have spindly processes because they are interconnected via desmosomes (star-shaped cells)
- hydrostatic tension in this structure maintains the Inner Enamel Epithelium in its correct shape
Dental Papilla
- structure formed form the condensed mesenchymal tissue that occurred under the internal enamel epithelium surrounding the enamel organ
Bell stage - why named this
- enamel epithelium forms the shape of a bell
Ameloblasts
- outter most cells of the inner enamel epithelium in the bell stage
- will secrete enamel of tooth later
- cause the organization of the cells opposing them to become odontoblasts
Odontoblasts
- secrete predentin
- induced to organize/develop from dental papilla due to ameloblast
Cervical Loop
- portion of epithelium where inner + outer enamel epithelium meet
- position will correspond to base of anatomical crown of finished tooth
What is the 1st event to occur in the Bell stage WRT root formation
- upon their completed organization odontoblast secrete predentin (highly susceptible to mineralization once extracellular –> to become dentin) on the side facing ameloblasts
- internal to dentin the dental papilla is now called pulp cavity
- mineralized matrix of dentin is highly eosinophilic (predentin is less)
Pulp Cavity
- previously was the dental papilla
- contains mesenchymal cells, extensive vascularization, innveration
- surrounded by ondontoblast layer (also derived from mesenchyme)
Dentinal Tubules
= fine processes of odontoblasts that remain embedded in dentin
- radially oriented structures
What is the 2nd event to occur in the Bell stage WRT root formation
- formation of enamel by the ameloblasts
- once they sense deposition of dentin against their apical surface they begin secreting the enamel matrix
Enamel and its morphology in common histological preparations
= most highly mineralized tissue in body
= 95% mineral
- histologic sections are routinely demineralized so 95% of enamel is removed in slides
What is the 3rd event to occur in the Bell stage WRT root formation
= formation of the root
- epithelium extending past cervical loop = Hertwig’s Root Sheath
- cells in this area are distinct from ameloblasts (in that they do not produce enamel) but they do cause the formation of the dentin-producing odontoblasts layer
- the root sheath stays in a relatively fixed position so as the root grows the tooth is pushed upward
What is the 4th event to occur in the Bell stage WRT root formation
- Rooth sheath epithelium becomes discontinuous
- and against outer surface of dentin is now exposed to mesenchymal tissue - cementoblasts
- cementoblasts produced the third mineralized tissue of the tooth = cementum
- as they do this they are trapped in the cementum and called cementocytes
Cementum
= avascular tissue
- needs a blood supply which is gets from PDL
- 2 types/regions of cementum
1) Acellular cementum
2) Cellular cementum
Gingiva
= specialized oral mucosal layer
- surrounds the tooth
= epithelium + CT
- the junctional epithelium = the portion of the gingival epithelium directly apposed to the enamel
Acellular Cementum
= founds nearest to the dentin
- where cementocytes have least access to source of nutrition and are the least active
Periodontal ligament (PDL)
= dense regular CT adjacent to cementum - organized obliquely or perpendicularly to it
- trasmits force of mastication to eh bone which absorbs it
- Sharpey’s Fibers - extend perpendicularly from PDL into both sides to connect into the cementum and bone
