Week 1: oral cavity microanatomy

Question 1

Components of the lip

Answer 1

1. External: thin skin, keratinized stratified sq. epithelium, has sweat glands, hair follicles, sebaceous glands
2. Vermillion zone: pink, thin epithelium, close vessels underneath. No sweat glands, follicles
3. Internal surface: mucosal surface. Wet epithelium, lined by stratified squamous, non keratinized epithelium

Question 2

Four types of papillae on tongue

Answer 2

1. Filiform: numerous, smallest. Conical projections of CT with overlying epithelium. No taste buds.
2. Fungiform: mushroom shaped. Can contain taste buds
3. Circumvallate: Large, dome shaped. Anterior to sulcus terminalis. 8-12. surrounded by moat like invagination lined by taste buds. lingual salivary glands (von Ebner’s) empty into moats.
4. Foliate: parellel rows in postero-lateral aspect of tongue, contain taste buds until 2-3 years old.

Question 3

Cell types of taste buds

Answer 3

1. neuroepithelial cells: receptors that transmit taste sensation via CN7 and 9
2. Supporting cells
3. Basal cells

Question 4

Taste buds

Answer 4

• respond to salty, bitter, sour, sweet and umami (MSG)

- tastant must be soluble and penetrate taste pore

Question 5

Structural components of teeth

Answer 5

1. Enamel: produced by amelobalsts.
2. Dentin: produced by odontoblasts. Calcified, but not as hard as enamel.
   - predentin: newly secreted
   - odontoblasts have cytoplasmic processes embedded in dentinal tubules
3. Cementum: covers root of tooth. Avascular, thin layer of bone like material secreted by cementocytes.
4. Periodontal ligament: collagen fibers, embed into bony matrix of socket wall. Attaches tooth in its socket
   - fibers oriented so resist forces that pull or compress tooth. Sensory receptors in ligaments sense tension.
5. dental pulp/pulp cavity: CT, vascularized richly, nerves enter into here through apical foramen

Question 6

Teeth development

Answer 6

• Ameloblasts from oral ectoderm
• odontoblasts (secreting dentin) from neural crest mesoderm.
• after tooth erupts, ameloblasts are absent. Enamel no longer produced.

Question 7

3 major salivary glands

Answer 7

1. Parotid: Serous
   - serous cells have round nuclei
2. submandibular: mixed but mostly serous
   - some mucous acini have cap of serous cells called serous demilunes
3. sublingual: primarily mucous
   - mucous cells have flattened nuclei, paler staining foamy cytoplasm

Question 8

Salivary Ducts

Answer 8

1. Intercalated ducts: first drain acini. cuboidal epithelium. add bicarb and absorb Cl-. Seen in serous/mix glands, hard to identify in mucous glands.
2. Striated duct: numerous infoldings, becomes more columnar, specialized for reabsorption of fluid and electrolytes
3. Excretory duct: embedded in CT. Stratified cuboidal or columnar. open into oral cavity

Question 9

Functions of saliva

Answer 9

• moisten oral mucosa
• moisten dry food to aid swallowing.
• provides a medium for dissolved & suspended food materials that chemically stimulate taste buds.
• buffer contents of the oral cavity via [HCO3]
• controls bacterial flora via lysozyme
• source of calcium & phosphate ions essential for normal tooth development &maintenance.
• antibodies & other anti-bacterial agents work against tooth decay.