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Oral Cavity Histology

Notes

Oral Cavity Histology

Lingual papillae of the Tongue

Lingual papillae cover 2/3rds of its anterior surface; lingual tonsils cover its posterior surface.

There are three types of lingual papillae:

  • Filiform, fungiform, and circumvallate; a 4th type, called foliate papillae, are rudimentary in humans.
  • Surface comprises stratified squamous epithelia
  • Core comprises lamina propria (connective tissue and vasculature)
  • Skeletal muscle lies deep to submucosa; skeletal muscle fibers run in multiple directions, allowing the tongue to move freely.
  • Taste buds lie within furrows or clefts between papillae; each taste bud comprises precursor, immature, and mature taste receptor cells and opens to the furrow via a taste pore.

Distinguishing Features:

Filiform papillae

  • Most numerous papillae
  • Their role is to provide a rough surface that aids in chewing via their keratinized, stratified squamous epithelia, which forms characteristic spikes.
  • They do not have taste buds.

Fungiform papillae

  • "Fungi" refers to its rounded, mushroom-like surface, which is covered by stratified squamous epithelium.

Circumvallate papillae

  • Are also rounded, but much larger and more bulbous.
  • On either side of the circumvallate papillae are wide clefts, aka, furrows or trenches; though not visible in our sample, serous Ebner's glands open into these spaces.

Dentition

Comprise layers of calcified tissues surrounding a cavity that houses neurovascular structures.

Key Features

Regions

  • The crown, which lies above the gums
  • The neck, the constricted area
  • The root, which lies within the alveoli (aka, sockets) of the jaw bones.
  • Pulp cavity lies in the center of the tooth, and extends into the root as the root canal.
  • Neurovascular structures pass through the apical foramen to reach the pulp cavity.

Layers

  • Dentin: comprises calcified organic matrix and inorganic hydroxyapatite crystals; this makes the dentin similar to, but harder than, bone.
  • Cementum: covers dentin in the neck and root regions; is anchored to the surrounding periodontal membrane by ligaments (not shown, here).
  • Enamel: covers the crown of the tooth; it comprises enamel rods (aka, prisms), and is the hardest material in the body.

Bony attachments

  • Sockets = alveoli
  • The periodontal membrane (aka, ligament) lies between the tooth and the bone
  • Gingiva epithelium covers bone (gingiva refers to the gums)
    • Gingival sulcus is the small space between the gingiva and the neck of the tooth. This space is enlarged in periodontal disease.

Salivary Glands

  • Comprise acini that secrete watery and/or mucous solutions with digestive enzymes.
    • These secretions are forced from the acini lumen, through intercalated and striated ducts, and, ultimately, into the oral cavity via main salivary ducts.
  • Myoepithelial cells encircle acini; these cells wrap around serous and mucous acini, and contract to force their secretions from the acini lumen into the ductile system.
  • Striated ducts receive secretions from intercalated ducts; these are distinguished by their striped appearance, which derives from basal interdigitations of cytoplasmic processes.

Parotid Gland

  • Lies in the cheek and is the largest salivary gland
  • Septum = ribbons of connective tissue that divide the glandular tissue into irregular-shaped lobes.
  • The lobular tissue = serous acini, which are clusters of cells that produce a watery substance.
    • At higher magnification, we would see the cytoplasmic zymogen granules that contain digestive enzymes and proenzymes.

Sublingual gland

  • Lies under the tongue.
  • Comprises light-staining mucous acini, which appear cloud-like in this sample.
    • Adipocytes may also be present; they are more prevalent in the glands of older individuals.

Submandibular gland

  • Lies under the lower jaw bone (the mandible)
  • Comprises a mix of light and dark acini
    • Mucous acini with serous demilune caps

Images:

Histology (Mark Braun, MD, & Indiana University: http://medsci.indiana.edu/c602web/602/c602web/toc.htm; http://www.indiana.edu/~anat215/virtualscope2/start.htm)