Microanatomy: oral cavity

Question 1

4 types of lingual papillae

Answer 1

• Filiform: most numerous, smallest, conical projections (small and pointy), no taste buds
• Fungiform: mushroom shaped, a little larger than filiform, numerous, do contain taste buds
• Circumvallate: very large, dome shaped, in a row that separates ant 2/3 from post 1/3
• Each one is surrounded by a moat that contain numerous taste buds, lingual salivary glands (von Ebner’s glands) empty serous secretions into the moats
• Foliate: folds on the lateral sides of the tongue near the circumvallate papillae that contain taste buds during early life but the buds are eventually lost (yr 2-3)

Question 2

Mechanism of taste detection (3 cell types)

Answer 2

• Neuroepithelial cells contain sensory receptors for tastant stimuli and transmit their signals to afferent nerves (7 or 9) that penetrate the taste buds
• These cells are surrounded by supporting cells and basal cells (the stem cell population)
• Taste is combination of sweet, salty, bitter, sour, umami
• To be tasted, the tastant molecule must be soluble and penetrate the taste pore of the taste bud in order to interact w/ receptors within the apical membrane microvilli of neuroepithelial cells

Question 3

Mucous vs serous secretions and functional roles of salivary ducts (besides conduits)

Answer 3

• Serous cells (protein-secreting): apical granules, round nuclei, indistinct cell boundary, darker cytoplasm
• Mucous cells (glycoprotein-secreting): paler foamy cytoplasm, flatter basal nuclei, distinct cell boundaries
• Intercalated ducts: mostly in serous or mixed glands, add bicarb and reabsorb chloride
• Striated ducts: cells have numerous basal infoldings (containing mito), reabsorb Na and secrete K (respond to ADH and aldo)

Question 4

3 different salivary gland histologies

Answer 4

• Parotid: all serous glands (densely dark staining cells)
• Submandibular: mixed gland, mostly serous
• Sublingual: mixed gland, mostly mucous

Question 5

Tooth development and embryologic origins

Answer 5

• Oral ectoderm cells become ameloblasts and form enamel (from the outside, ameloblasts are eventually lost and enamel is never replaced)
• Once tooth erupts ameloblasts are lost
• Neural crest cells become odontoblasts and form dentin
• Odontoblasts are retained and can continue to form dentin

Question 6

Elements of a tooth and pain/positioning detection 1

Answer 6

• Enamel: formed by ameloblasts (oral ectoderm) that are lost when tooth erupts
• Dentin and predentin: both are made by odontoblasts (neural crest), as the predentin is mineralized it turns into dentin (which is closer to enamel surface)
• Tomes fibers are tubes w/in dentin form odontoblast processes, these may serve as transducers that transmit pain stimuli to the nerve in the pulp
• Pulp cavity: CT compartment surrounded by dentin, very vascular and highly innervated (vessels and nerves enter pulp cavity via apical foramen), the nerves send networks into odontoblasts and dentinal tubules

Question 7

Elements of a tooth and pain/positioning detection 2

Answer 7

• Cementum: a thin layer of bone-like material (except it is avascular) that is secreted by cementocytes, in order to glue the tooth into surrounding periodontal ligament
• Periodontal ligament: collagen fibers that project out of cementum to dentin and then connect to the surrounding alveolar bone
• The fibers are arranged so that some fibers resist pulling while other fibers resist compression