12.2 - Lab + Lecture Notes

Question 1

Vermillion Border

Answer 1

= the transition zone in the lip between the SSK of the skin and the SSNK of the oral cavity

Question 2

Orbicularis Ovis

Answer 2

= skeletal muscle in the lip

• lies deep to the mucosa
• encircles the lip to form the 1st sphincter of the GI tract

Question 3

Filiform Papilla

Answer 3

• folds in tongue where the tufts of keratin extend perpendicularly away from epithelial surface

Question 4

Fungiform Papilla

Answer 4

• interspersed among the filiform papilla
• roughly the same size as the filiform papilla
• have shape of little mushrooms
• contain taste buds

Question 5

Circumvallate (Vallate) Papilla

Answer 5

• 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)

Question 6

Describe Tooth development in 4th month in two bullet points

Answer 6

• deciduous (baby teeth) begin to acquire enamel

- tooth germs of permanent teeth begin to form

Question 7

Describe the role of ectomesenchymal cells in tooth development

Answer 7

• 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

Question 8

Dental lamina

Answer 8

= 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

Question 9

Cap Stage - why is it named this (include an important organ)

Answer 9

= named for appearance of general shape of invaginated dental lamina –> forms enamel organ

Question 10

Enamel Organ

Answer 10

• 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

Question 11

Stellate reticulum

Answer 11

• 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

Question 12

Dental Papilla

Answer 12

• structure formed form the condensed mesenchymal tissue that occurred under the internal enamel epithelium surrounding the enamel organ

Question 13

Bell stage - why named this

Answer 13

• enamel epithelium forms the shape of a bell

Question 14

Ameloblasts

Answer 14

• 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

Question 15

Odontoblasts

Answer 15

• secrete predentin

- induced to organize/develop from dental papilla due to ameloblast

Question 16

Cervical Loop

Answer 16

• portion of epithelium where inner + outer enamel epithelium meet
• position will correspond to base of anatomical crown of finished tooth

Question 17

What is the 1st event to occur in the Bell stage WRT root formation

Answer 17

• 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)

Question 18

Pulp Cavity

Answer 18

• previously was the dental papilla
• contains mesenchymal cells, extensive vascularization, innveration
• surrounded by ondontoblast layer (also derived from mesenchyme)

Question 19

Dentinal Tubules

Answer 19

= fine processes of odontoblasts that remain embedded in dentin
- radially oriented structures

Question 20

What is the 2nd event to occur in the Bell stage WRT root formation

Answer 20

• formation of enamel by the ameloblasts

- once they sense deposition of dentin against their apical surface they begin secreting the enamel matrix

Question 21

Enamel and its morphology in common histological preparations

Answer 21

= most highly mineralized tissue in body
= 95% mineral
- histologic sections are routinely demineralized so 95% of enamel is removed in slides

Question 22

What is the 3rd event to occur in the Bell stage WRT root formation

Answer 22

= 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

Question 23

What is the 4th event to occur in the Bell stage WRT root formation

Answer 23

• 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

Question 24

Cementum

Answer 24

= avascular tissue

• needs a blood supply which is gets from PDL
• 2 types/regions of cementum
  1) Acellular cementum
  2) Cellular cementum

Question 25

Gingiva

Answer 25

= specialized oral mucosal layer - surrounds the tooth = epithelium + CT - the junctional epithelium = the portion of the gingival epithelium directly apposed to the enamel

Question 26

Acellular Cementum

Answer 26

= founds nearest to the dentin | - where cementocytes have least access to source of nutrition and are the least active

Question 27

Periodontal ligament (PDL)

Answer 27

= 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